Technical papers review of WIC nutritional risk criteria

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/i5&v United States
Department of
Agriculture Technical Papers
Food and
Nutrition
Review of WIC Nutritional
Risk Criteria
J
This set of Technical Papers on the "Review of WIC Nutritional
Risk Criteria" represents the final deliverable submitted in
August 1991 to the U.S. Department of Agriculture, Food and
Nutrition Service, by the University of Arizona, College of
Medicine, Department of Family and Community Medicine, under
Cooperative Agreement #58-3198-1-005. The papers were prepared
by Principal Investigator Gail G. Harrison, PhD, RD; and Co-
Investigators Osman M. Galal, MD, PhD; and Sheila H. Parker, MS,
MPH, DrPH; and the Research Assistants, April H. Dean, MS, RD;
Awal Dad Khan, MS; Laura Kettel Khan, MIM; Marc J. Morse, MD;
Magda A. Shaheen, MB, BCh, MSc; Amr S. Soliman MB, BCh, MSc; and
Sahar S. Zaghloul, MB, BCh, MSc.
August 1991
J
PREFACE
The Child Nutrition and WIC Reauthorization Act of 1989 (Public
Law 101-147) required the O.S. Department of Agriculture (DSDA)
to conduct a review of the nutritional risk criteria used in the
Special Supplemental Food Program for Women, Infants and Children
(WIC) and the relationship of such criteria to the Program's
participant priority system. The legislation specifically
directed the Department to consider the preventive nature of the
WIC Program and to examine risks to categorically eligible
persons, especially pregnant women, from conditions such as
homelessness, mental illness, and conditions that pose barriers
to the receipt of prenatal care and/or may increase the
probability of adverse pregnancy outcomes or other adverse
effects on health.
In designing the procedure for completion of the legislatively
mandated review, the Department was convinced that its
consideration of these important and complex issues would benefit
greatly from public participation. Therefore, a Hotice was
published in the Federal Register on September 14, 1990 which
identified the major issues to be addressed by the review and
solicited public input on these issues. A copy of the Notice is
included with the attached technical papers as background
material.
The second phase of the review process involved enlisting
independent technical experts to review the comments submitted to
USDA in response to the Notice and then to conduct a
comprehensive search of the scientific literature available on
the issue topics to determine whether a consensus or majority
opinion could be established on each one.
The attached technical papers were then developed by a team of
professors and graduate students at the University of Arizona's
College of Medicine, Department of Family and Community Medicine,
under a Cooperative Agreement with USDA's Food and Nutrition
Service during the spring and summer of 1991. Drafts of the
papers were provided to the National Advisory Council on
Maternal, Infant and Fetal Nutrition for discussion at an ad hoc
meeting of 12 Council volunteers in June 1991. The papers were
then revised, resubmitted to the Department, and used to form the
agenda of a full Council meeting in September 1991, along with
similar papers developed as part of a separate review addressing
the foods prescribed provided to participants by the WIC Program,
which was also mandated by Pub. L. 101-147.
The Council's recommendations are included in its 1992 Report to
Congress and the President. Copies of the Report are available
upon request from the U.S. Department of Agriculture, the Food
and Nutrition Services, Supplemental Food Programs Division, 3101
Park Center Drive, Room 540, Alexandria, Virginia 22302,
(703) 305-2730.
INTRODUCTION AND OVERVIEW
The purpose of this introduction and overview is to describe the background for and
general methodological approach used in the production of an accompanying set of
fifteen (15) brief, focused technical papers prepared for the U.S. Department of
Agriculture, Food and Nutrition Service, Supplemental Food Programs Branch, under a
cooperative agreement with the University of Arizona. The papers were prepared
between March and August 1991. Drafts were reviewed by a subcommittee of the
National Advisory Committee on Maternal, Infant and Fetal Nutrition (NAC) and by FNS
staff, and the final documents were reviewed and discussed by NAC at its meeting in
September 1991.
The WIC Program
The Child Nutrition Act of 1966, as amended, established the Special Supplemental
Food Program for Women, Infants, and Children (WIC Program) based on growing
evidence that nutritional inadequacy is linked to compromised physical and mental
development, and that nutritional supplementation could result in positive health
improvements when targeted to low-income pregnant and postpartum women and
preschool children who are at nutritional risk. The program serves as both an adjunct to
health care and an entry into health services for many women and children during
critical periods of growth and development. The program provides four types of
services to clients, free of direct cost: nutritional and general health assessments;
nutrition education; health care and other public assistance referrals, as appropriate; and
food benefits, through specified supplemental food packages, which may be provided
via vouchers, direct home delivery, or direct distribution. Administered federally by the
Food and Nutrition Service (FNS) of the U.S. Department of Agriculture (USDA), the
program is managed at the state level by health agencies in the 50 states, Puerto Rico,
the Virgin islands, and the District of Columbia, and by Indian Tribal Organizations which
function as state agencies. As of September 1991, the WIC program was serving
approximately 5.1 million individuals; about 23% were women, 31% were infants and
46% were preschool children.
Eligibility for the program is based both on income criteria and on nutritional risk criteria.
The legislation defines "nutritional risk" as "(A) detrimental or abnormal nutritional
conditions detectable by biochemical or anthropometric measures; (B) other documented
nutritionally related medical conditions, (C) dietary deficiencies that impair or endanger
health, or (D) conditions that predispose persons to inadequate nutritional patterns or
nutritionally related medical conditions, including but not limited to alcoholism and drug
addiction." These criteria not only assure that the entire program is targeted to those
most likely to benefit from it, but also serve as the basis for a priority system which
state and local agencies can use to allocate their resources when funding does not
permit serving all eligible clients. The priority system currently in use is as follows
(Federal Register 55(179): 37683, 9/14/90):
Priority I. Pregnant and breastfeeding women and infants as demonstrated by
documented nutritionally related medical conditions.
Priority II. Except those infants in Priority I. Infants up to six months of age born
of women who were program participants during pregnancy or who were at nutritional
risk during pregnancy due to documented nutritionally related medical conditions.
Priority III. Children at nutritional risk as demonstrated by documented nutritionally
related medical conditions.
Priority IV. Pregnant and breastfeeding women and infants at nutritional risk due to
an inadequate diet.
Priority V. Children at nutritional risk due to an inadequate diet.
Priority VI. Post part urn women at nutritional risk (state agencies have the option of
defining "high-risk" postpartum women and placing them in Priorities III, IV, and/or V).
Priority VII. (State agency option). Previously certified participants who might
regress in nutritional status without continued provision of supplemental foods.
In practice. State agencies have had considerable latitude in defining specific criteria
within the broad legislative parameters, and the criteria in use vary from state to state.
Several agencies, including the General Accounting Office, have expressed some
concern about consistency of targeting criteria. The National Advisory Council (NAC)
on Maternal, Infant and Fetal Nutrition recommended that FNS issue guidance to state
agencies for use in development and evaluation of nutritional risk criteria.
Selection of Issues for the Technical Papers
The current work was undertaken as part of a Congressionally-mandated review of the
nutritional risk criteria by the Department of Agriculture.
A notice of the review was published in the Federal Register in September 1991, and
public comments solicited. A total of 184 written comments were received, from state
and local WIC agencies and personnel, public interest groups, professional organizations,
industry, and the general public. The first part of the present scope of work was to
review and summarize those comments; that summary was provided to USDA/FNS in
March 1991. The summary of comments and input from FNS staff formed the basis for
identification of many of the issues for the technical papers. The issues selected
represent those which are of concern to commenters and those for which USDA/FNS
program staff indicated a need for technical background information. Several major risk
factors for malnutrition and/or poor pregnancy outcome were not addressed, since FNS
felt that sufficient scientific consensus was already available.
Identification of Relevant Literature
Once the key issues were tentatively identified and the number of papers to be drafted
decided, literature searches were undertaken by standard means through computerized
searches of the National Library of Medicine database. Unpublished documents and key
reports were also obtained when their availability became known, as supplements to the
literature accessible through standard searches, directly from the source or author's
courtesy. Searches were not limited to U.S. studies, but rather took advantage of the
worldwide literature when it could address issues of interest. The literature search was
limited to the English-language literature. We utilized the expertise of several
consultants who were able to direct us to several important documents which were in
press at the time. In addition, USDA/FNS staff were able to locate and share with us
several important unpublished reports.
Evaluation of the Quality of Literature Available on Kev Issues
There is considerable variability by topic in the amount, recency, and quality of existing
scientific information on the issues addressed by the technical papers. Therefore, no
hard and fast rule was made about what types of studies would be included in the
overall review. On topics for which there was an abundance of relevant literature,
recent, peer-reviewed studies with the most appropriate design for investigating the
topic were given priority in emphasis. On other topics (e.g., pica in pregnancy) most of
the published literature is quite old, some is very anecdotal, and there is a relative lack
of recent studies. On still others (e.g., homelessness), scientific interest in the topic is
relatively recent and it was necessary to include some information from reports and
other unpublished documents rather than to rely entirely on peer-reviewed publications.
Our strategy for coping with this unevenness by topic was simply to be clear within
each paper about the quality of literature. Where there are significant methodological
problems with a study, they are mentioned. Where the literature is less than ideal to
address the topic, this is mentioned. Studies which are central to a given issue are
described in some detail, and when comparisons among studies are made the
differences in their design are pointed out.
Development of Technical Papers
Each paper was first drafted by the primary author and then reviewed by a faculty team
and revised. Revised papers were provided as draft documents to USDA/FNS and to
consultants. Several consultants and the USDA/FNS Program Officer for the project
traveled to Tucson for a two-day meeting, during which each draft paper was discussed
in detail. Following this meeting, the drafts were again revised and made available to a
subcommittee of the National Advisory Council on Maternal, Fetal, and Infant Nutrition
(NAC). The investigators met with that subcommittee in June 1991 for a full day, and
again each paper was discussed in some detail. Following that meeting there was some
minor rearrangement of topics. We again asked consultants' advice on specific papers.
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updated information on one or two topics on which very recent publications or
recommendations had become available, and once again revised the papers.
In each paper, we have attempted to make clear where there is scientific consensus on
a given topic; where there is disagreement; where the state of the art is evolving very
rapidly; and where the quality of evidence is either poor or difficult to evaluate.
Acknowledgements
The following consultants gave generously of their time and expertise to this project.
We are most grateful.
Lindsay H. Allen, PhD (University of Connecticut)
Richard Naeye, MD (Pennsylvania State University)
Hector Balcazar, PhD (Arizona S' ate University)
Peter Dallman, MD (University of California, San Francisco)
WIC NUTRITIONAL RISK TECHNICAL PAPERS
#1 Anthropometric Standards for U.S. Children
#2 Anthropometric Assessment of Pregnant Women
#3 Overweight and Obesity in Pregnancy
#4 Overweight and Obesity in Infants and Children
#5 Hematologic Standards for Risk of Iron Deficiency
#6 Age and Primiparity as Risk Factors to Poor Pregnancy
Outcome in U.S. Women
#7 Evidence for Effects of Timing of Prenatal Care and
Nutritional Supplementation on Pregnancy Outcome
#8 Passive Smoking: What is the Evidence for Health Effects?
#9 Nutritional Risk Implications of Pica in Pregnancy
#10 Intake of Caffeine and Related Compounds: Evidence of
Nutritional Risk?
#11 Drug Use and Nutritional Risk in Pregnancy
#12 Homeless Mothers and Children: What is the Evidence
for Nutritional Risk?
#13 Appropriate Dietary Assessment Methodology for the WIC
Clinic Setting
#14 Pica and Lead Exposure in Infants and Children: Health and
Nutritional Risk Implications
5"
Technical Paper 1
Anthropometric Standards for U.S. Children
Technical Paper #1 prepared for the U.S. Department of Agriculture, Food and Nutrition
Service, under Cooperative Agreement #58-3198-1-005, "Review of Nutritional Risk
Criteria for the WIC Program", with the Department of Family and Community Medicine,
University of Arizona, by Gail G. Harrison, PhD and Sahar S. Zaghloul, MB, BCh, MSc. Dr.
Harrison is Professor of Family and Community Medicine, College of Medicine; Dr. Zaghloul
is Research Assistant, Department of Family and Community Medicine and a doctoral
candidate in Nutritional Sciences, University of Arizona, Tucson, Arizona 85724.
August 6, 1991
U>
INTRODUCTION
The Special Supplemental Food Program for Women, Infants and Children (WIC) includes
anthropometric criteria for defining nutritional risk in children which vary somewhat among
geographical state agencies. These criteria are limited to those which can be addressed by
measures of height, weight and age. All include low birth weight (<2.5 kg or 5.5 lb) as a
criterion; all include some definition of low height-for-age, low weight-for-height, and high
weight-for-height for infants and children up to the age of five years. The questions of
relevance for the present paper are the following:
a) is 2.5 kg the best cutoff point for identifying nutritional risk in newborns in the U.S.?
b) how does variation in the distribution of anthropometric measures among the
different racial and ethnic groups in the U.S. affect the utility of a single reference standard
for purposes of identifying nutritionally at-risk children? and
c) what are the consequences of different cutoff points relative to the reference
standard for different racial/ethnic groups?
The objective of this paper is to review the information which is available to address these
issues for the U.S. population.
THE IDENTIFICATION OF NUTRITIONAL RISK BY WEIGHT AT BIRTH
The internationally accepted cutoff for "low birth weight" is 2500 grams, or 5.5 pounds.
Below this weight, infant mortality rises dramatically. However, it is important to
appreciate that this may not be the optimal cutoff for identifying the infant whose growth
has been constrained by nutritional factors. There are many potential causes for low birth
weight, broadly falling into: a) prematurity (birth before 38 weeks of gestation), and b)
intrauterine growth retardation (IUGR), which may be caused by a variety of factors
including maternal undernutrition and other maternal variables which can constrain delivery
of nutrients to the fetus. IUGR is identified by weight for gestational age at birth relative to
standard reference data. (The issue of appropriate reference data for identifying IUGR in
U.S. infants is of considerable scientific and clinical importance, but will not be addressed
in this paper since it cannot be readily assessed within the structure of the WIC program).
IUGR can be further divided into proportional vs nonproportional growth retardation - i.e.,
the fetus who has suffered growth retardation throughout gestation and whose length and
weight are proportionately low at birth for gestational age, vs the fetus whose weight is
decreased but whose length is relatively less affected, reflecting nutrient deprivation
primarily in the last trimester. The distinction can be made on the basis of the ponderal
index (Roher's Index), weight/length3. The former type of IUGR (proportionate) is
associated with substantially greater neonatal mortality, particularly for term infants
(Balcazarand Haas, 1990, 1991).
Changes in mean birthweight within a population may be important and reflect nutritional
risk even if there is no change in the low birthweight rate. The lowest risk of infant
mortality is associated with birth weights of 3500-4000 grams, and any increase in the
proportion of birthweights below 3500 grams may increase infant mortality (Kramer,
1987). Balcazar and Haas (1991), in a study of 9660 newborns in Mexico City, found that
1
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term infants weighing less than 2900 grams (the 10th percentile of weight for gestational
age for term infants based on a composite of several U.S. and European reference
standards) had a neonatal mortality risk of 29.0 per 1000, compared to 2.8 per 1000 for
term infants whose weight was appropriate for gestational age. Lester et al. (1986) found
striking behavioral differences in the immediate postnatal period (18-60 hours after birth)
between normal-weight term infants (mean birthweight 3186 grams) and small-for-gestational-
age infants (average birthweight 2737 grams) in Puerto Rico; newborns who
were small-f or-age were less responsive, less able to process visual and auditory stimuli,
and exhibited more immature motor development than heavier neonates.
There is also evidence that IUGR resulting in birthweights low for gestational age but above
2500 grams has consequences for neurological and behavioral development and for
postnatal growth potential. Kimball et al. (1982) compared the long-term growth and
development of three groups of infants: normal birth weight for gestational age (3266 _±.
362 g) and normal ponderal index; low birth weight for gestational age (2600 _± 276 g)
and low ponderal index (IUGR-LPI); and low birth weight (2600 ±_ 189 g) and normal
ponderal index (IUGR-API). At three years of age, the IUGR-API group remained lighter and
shorter than other children, and had smaller head circumference; they were also at greater
developmental risk. Long-term effects on postnatal growth and behavioral development
were greatest for very low-birthweight (_< 1500 g) infants; intermediate for IUGR-API
infants; and smallest but still apparent for IUGRD-LIP infants. Largo et al. (1989)
investigated the significance of prenatal, perinatal and postnatal variables on neurological,
intellectual and language development at age five to seven years. Prematurity had a much
larger influence on neurological and intellectual development at age 5-8 years, but children
who had been full-term but underweight newborns were more likely to exhibit behavior
problems.
In summary, intrauterine growth retardation is often manifested for term infants as
birthweight low for gestational age but above the standard 2500-gram cutoff point; it does
reflect prenatal undernutrition and there is good evidence that there are long-term effects
on development and on physical growth potential.
ANTHROPOMETRIC STANDARDS FOR GROWTH OF INFANTS AND CHILDREN
The most available and well accepted reference standard available for use on a national
basis for assessment of anthropometric measures in infants and children is that of the
National Center for Health Statistics (Hamill et al., 1979), which has also been adopted for
international use (WHO, 1987). The data are based on nationally representative samples of
children over age two years, and below two years on the Fels Longitudinal Growth Study
data. The latter data are from healthy, Caucasian children in Ohio and thus may not be
representative of the growth of other groups of children; the data on older children while
nationally representative may be less than optimal for specific subgroups within the
population. There are considerable advantages, however, to using a consistent standard
for evaluation of growth even though cutoff points may be set differently for different
purposes.
Most WIC programs use percentiles of the reference standard to designate risk cut-off
points. The scientific literature on nutritional status tends to use Z-scores or standard
deviation units, which are more useful in quantifying differences in very malnourished
H
populations. Figure 1, from Frisancho (1990) shows equivalencies among Z-scores and
percentiles.
Z Score or S.D.
Percentile
Figure 1 Schematization of the statistical relationship of Z-scores,
percentile ranges, and standard deivations. Modified
from Frisancho, 1990.
RACIAL/ETHNIC VARIATION IN THE DISTRIBUTION OF ANTHROPOMETRIC INDICES OF
GROWTH
For a nationwide program which uses snthropometric measures as evidence of nutritional
risk, it is important to appreciate whether the differences among racial and ethnic groups
are substantial within the age range of interest and if so, whether they can be assumed to
be due to genetic rather than nutritional factors.
Black. White and Hispanic Children
Tables 1-3 (constructed from data in Frisancho, 1990 and NCHS, 1989) summarize
available data for nationally representative samples of White and Black children from the
second National Health and Nutrition Examination Survey (NHANES II, 1975-80) and,
where the numbers are adequate for Mexican-American and Puerto Rican children from the
Hispanic Health and Nutrition Examination Survey (HHANES, 1982-84). Shown are means,
standard deviations, and percentile distributions for stature (Table 1), weight (Table 2) and
body mass index or Quetelet's index (weight/stature3) (Table 3). While the Body Mass
Index is less often used clinically than is weight-f or-height as a percent of median expected
or as a percentile, it gives essentially the same information. Inspection of these tables will
reveal very minimal variation in mean and median values for weight or height among ethnic
groups. Only one difference appears to be large enough to be of interest; the fifth
percentile for stature is a full two centimeters lower for Black than for White children age
one to two years, and persists for boys at the age of 2-2.9 years, but the difference is no
longer evident after three years of age.
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9
The numbers of Hispanic children included in the data from which Tables 1-3 were derived
are too small to make firm conclusions about weight-for-height distribution; and Native
American and Oriental children are not included (NCHS, 1989).
Native American Children
Native American children clearly have an excess of high weight-for-height compared to
other groups of children (Harrison and Ritenbaugh, in press; Sugarman et al., 1990; Owen
et al., 1979; Peck et al., 1987). The prevalence of adult obesity, and obesity-related
diabetes, among some Native American tribes is also extremely high. Sugarman et al.
(1990) studied school-aged Navajo children in 1989, twenty years after a survey done in
the same area, and documented increases in stature-for-age for both boys and girls, and
much greater increases in weight-for-age for both sexes. Thus while the prevalence of
obesity seems to be increasing dramatically among Navajo children, there is also evidence
of a secular trend in stature in this group. In contrast Owen et al. (1979) in a follow-up
study of White Mountain Apache preschool children in 1976, found that compared io a
comparably sampled 1969 cohort, there was no increase in height but a significant increase
in skinfold thickness. That the relatively high weight-for-height distribution among Native
American children is characteristic of very young children is seen in the study of Harrison
and White (1981), who analyzed Arizona nutrition surveillance data and found that
controlling for birth weight. Native American children had substantially higher weight-for-height
in the second year of life than Mexican-American children, who in turn had higher
weight-for-height indices than Anglo (non-Hispanic white) children. Length-for-age was not
different among the three groups, nor affected by birth weight by age 13-24 months.
Mexican-American Children
Mexican-American children, who genetically represent a mixture of European White and
Native American background, also tend to have relatively short stature and high relative
weights (Martorell et al., 1987; Yanochick-Owen and White, 1977; Kautz and Harrison,
1981; Harrison and White, 1981; Dewey et al., 1983; Malina et al., 1983). Overall,
greater chest circumference, trunkal skinfolds, and overall fatness seem to describe the
Mexican-American child relative to non-Hispanic White children and Black children. In the
NHANES I and II data, short stature is related to poverty among Whites, Blacks, and
Mexican-Americans; relative weight among Mexican-Americans had no relationship to
economic status (Martorell et a' . 1987). In the more recent Hispanic HANES survey;
neither stature nor relative weight was different between poor and nonpoor Mexican-
American children, however (Ryan et al, 1990). Martorell et al. (1989) and Roche (1990)
have compared age- and sex-specific weight and stature percentiles for Mexican-American
children from the HHANES data with those of White children in the NHANES II data. Until
adolescence, there were no significant differences for boys; for girls, the 50th and 95th
percentiles for weight were significantly higher for Mexican-Americans.
Asian-American Children
Asian-American children, particularly refugee groups who immigrated from Southeast Asia
in the late 1970s and early 1980s. pose particular problems of interpretation and for states
in which these subgroups have settled, may raise questions of interpretation of reference
JO
Figure 2
Short Stature by Age/Ethnic Group
1989 Pediatric Nutrition Surveillance
Total States/Temtories/Reservatioru
PERCENT <5TH PERCENTTLE
20 T-
•5
1011411 WHITE SLACK HISPANIC INDIAN ASIAN
I'll' §■ I y< ■i-<r'l
Nmooil PrevalMM ■ 9.6*
Figure 3
Underweight by Age/Ethnic Group
1989 Pediatric Nutrition Surveillance
Total Staies/Territories/Reservatioru
PERCENT <5TH PERCENT1LE
8
Wei|hl/Hei|ht
WHITE BLACK HISPANIC INDIAN
CD •< v Hi i y ■■ 2-4 »r■
NllionaJ Prevalence - 3.2ft
ASIAN
Figure 4
Overweight by Age/Ethnic Group
1989 Pediatric Nutrition Surveillance
Total States/Territories/Reservations
PERCENT <95TH PERCENTILE
20
IS-
10'
5'
Wwgfcc/Hwghi
tt.< 1kii WHITE BLAO HISPANIC INOIAN ASIAN
CD"»' ■■ ' »' ■!•' <'l
Ntiioul Prevaltttcc -9 3%
ti
Countsv Div««i«n of Nmnirtn Center* fnr 1i«» f*nflfml
standards. Too little data are available currently to make firm conclusions about the normal
growth patterns for children belonging to these groups. Early reports of their nutritional
status showed high rates of apparent malnutrition, manifested as anemia and stunting
(Peck et al., 1981). Recent data from the Centers for Disease Control Pediatric Nutrition
Surveillance System (GAO, 1990) show increasing height-for-age and decreasing
prevalence of low height-for-age in Asian-American children between 1981 and 1989.
CONSEQUENCES OF PARTICULAR CUTOFF POINTS FOR HEIGHT-FOR-AGE AND WEIGHT-FOR-
HEIGHT FOR DIFFERENT RACIAL/ETHNIC GROUPS
Figures 2-4 present data on the prevalence of low height-for-age, low and high weight-for-height,
defined at the 5th or 95th percentile, by ethnic group from the Centers for Disease
Control Nutrition Surveillance System (1989), for children of the WIC target group age.
This database is derived from more than 4000 local clinics including health department
clinics, WIC clinics, and Indian Health Service clinics, in 43 geographical units including
states, the District of Columbia, Puerto Rico, and Indian tribal units. The relative excess of
low height-for-age among White children can be taken as evidence for the low-income
nature of the population from which these data were derived. Prevalences of height-for-age
below the 5th percentile are highest for Black infants under one year, Hispanic children
one to two years, and Asian children older than one year. There is a lower-than-expected
prevalence of low weight-for-height in all subgroups. The prevalence of high weight-for-height
(above the 95th percentile of the NCHS reference population) is higher among Black,
Hispanic, and Native American children than in White or Asian children. None of the ethnic
groups, however, shows a prevalence of high weight-for-height so great as to include a
large share of the population screened. Very likely the differences seen represent real
differences in the prevalence of obesity.
CUTOFF POINTS FOR RISK ASSESSMENT
The reference population is assumed to consist of healthy, normal children whose attained
growth represents their genetic potential. If a screened population were exactly the same
as the reference population, then, for example, five percent of children would have heights
at or below the 5th percentile. If a screened population has an excess of children with
height-for-age below a cutoff point (e.g., 10 percent below the 5th percentile), we assume
that the difference (5 percent) represents short stature due to environmental causes and is
likely to be responsive to nutritional and health intervention. The remaining five percent of
children are healthy and normal and will not respond to nutritional intervention. When the
ratio of affected to normal children identified is high and the intervention is without risk, we
simply accept the false positives (healthy children identified as eligible but who will not
respond).
The fifth percentile as a cutoff point for identification of short stature and low weight for
height is in common use and has been recommended by a number of experts, albeit
arbitrarily (Robbins and Trowbridge. 1984; Zerfas et al., 1977; DHHS, 1981). If a cutoff
point is set at a higher level (e.g., the 10th or 25th percentile) it may be possible to identify
additional children at nutritional risk, but at the cost of a higher rate of false positives
(misclassification of normal children). As the cutoff becomes more liberal, the proportion of
healthy children to malnourished ones identified rises. Thus if a screened population
includes 30% of children below the 25th percentile for height, we may assume that only
5
ia
one in six of these will respond to nutritionsl intervention. The choice of cutoff points for
defining risk, therefore, will depend on resources end priorities within the progrsm.
It msy not be possible to judge on s cross-sectionsl basis whether a highly prevalent
condition (e.g., short stature, or high weight-for-height) will respond to nutritional
intervention. Useful surrogate information, when it is available, includes whether there is
an income relationship with the measure and whether there are demonstrable secular trends
occurring in the measure. Either situation is a good argument for high prevalence being the
result of nutritional etiology. It may be useful to point out that cutoff points for low and
high weight-for-height need not be symmetrical, since their use is to identify two quite
different conditions.
SUMMARY
There is good reason to consider birthweights above 2500 grams but low for gestational
age as a marker for nutritional risk, as they reflect both prenatal undernutrition and
postnatal risk for increased mortality and for impaired growth and development. A
reasonable cutoff point for full-term infants would b 2900 grams, which reflects
approximately the tenth percentile of weight for gestai onal age at term from a composite
of several U.S. and European references standards.
There are demonstrable differences in the distribution of heights and weight-for-height
among children of different ethnic and racial groups in the U.S. Among U.S. ethnic groups,
there is enough variation to result in the inclusion of large proportions of Asian children as
short-for-age relative to national standards and a relatively large proportion of Hispanic and
Native American children as heavy-for-height. There is insufficient evidence to suppose
that either of these phenomena is not influenced by the nutritional environment, particularly
in view of the fact that both phenomena show some evidence of secular trend - i.e., that
height is increesing in some groups of the population and that high weight-for-height is
increasing among children in the population as a whole. There is no reason not to use the
current national and international reference standard, namely the National Center for Health
Statistics reference, for screening in the WIC program in spite of the fact that the data
were derived from children who are not representative of the various ethnic groups which
now comprise the U.S. population.
Designstion of cutoff points for anthropometric meesures must consider the resources
available and the potential responsiveness of reel cases of nutrition-related short stature,
low weight-for-height and obesity to the interventions which are provided by the program.
More conservative cutoff points, generally speaking, will increase the ratio of cases to false
positives and improve targeting while more liberel cutoff points will increase the number of
at-risk children served overall. It may be edvisable to consider asymmetric cutoff points for
low and high weight-for-height, depending on the population served and program resources.
6
IS
Table l
MEANS, STANDARD DEVIATIONS, AND PERCENTILES OF STATURE (on) BY AGE (yrs)
FOR MALE AND FEMALE CHILDREN AGES 1-5 YEARS OF DIFFERENT ETHNIC GROUPS
Age
<y«) Race Sex N Mean SD
Percent iles
5
74.3
73.9
10 15 25 50 75 85 90 95
94.0
87.4
1.0-1.9
Black MF
77
56
82.3
81.0
5.4
4.0
76.1
75.7
77.5
77.4
79.0
78.3
81.7
81.2
86.0
83.0
87.2
84.3
89.5
87.0
While MF
277
264
82.5
80.5
5.0
4.9
75.7
73.0
76.8
74.7
77.9
75.6
79.4
76.9
82.2
80.2
85.6
83.6
87.2
85.8
88.0
86.8
89.2
88.4
Mexican
American
MF
104
118
82.6
80.7
4.6
4.8
76.C
74.2
76.8
75.1
77.4
76.6
79.3
77.6
82.1
80.4
85.3
84.0
87.9
85.1
88.8
86.5
90.1
87.5
Puerto
Rican
MF
31
31
83.2
82.0
7.1
6.8
- -
-
77.8
79.1
83.6
83.3
86.7
86.7
- -
-
2.0-2.9
Black MF
139
118
90.7
90.0
4.7
5.1
83.5
81.5
84.8
84.6
85.8
85.1
87.2
86.5
90.1
89.8
94.2
93.2
96.0
95.0
96.8
96.7
98.0
97.9
White MF
504
479
91.7
90.2
4.2
4.4
85.8
83.4
86.8
84.9
87.5
85.7
88.9
86.9
91.7
90.2
94.4
93.0
95.8
94.5
97.0
95.7
98.3
97.4
Mexican
American
MF
no
116
91.5
89.2
4.0
3.8
85.1
82.7
86.1
84.5
87.2
85.6
88.9
86.9
91.7
89.4
93.8
91.9
95.6
93.4
96.6
94.0
98.2
94.4
Puerto
Rican
MF
34
27
151
126
93.4
88.9
5.3
4.1
90.2
92.3
93.0
93.1
-
89.1
85.8
94.0
88.1
96.6
91.6 •
- -
3.0-3.9
4.0-4.9
Black MF
99.1
98.6
5.4
4.7
94.3
94.2
95.8
95.3
98.3
98.5
102.5
101.0
104.5
102.7
106.7
103.7
108.4
105.7
White MF
540
509
99.1
97.5
4.5
4.5
92.0
90.1
94.0
91.6
94.8
92.7
96.3
94.6
98.8
97.4
102.0
100.5
103.8
102.3
104.8
103.4
106.3
104.5
Mexican
American
MF
131
97
98.6
97.9
4.8
4.6
89.7 91.2
90.0
93.3
92.6
95.6
94.2
99.5
98.4
101.7
101.6
103.6
102.3
104.2
103.6
105.5
Puerto
Rican
MF38
40
99.5
98.0
4.7
3.9
5.7
5.1
-
99.6
100.0
94.9
93.2
95.6
95.9
99.0
97.6
102.3
100.6
104.1
101.6
- -
Black MF
151
147
107.1
106.6
98.1
98.4
101.3
101.3
103.5
103.1
107.7
106.6
110.7
109.8
112.4
111.9
113.7
113.9
116.7
115.0
White MF
547
519
105.7
104.5
4.8
4.8
98.3
96.2
99.6
98.3
100.6
99.4
102.6
101.3
105.7
104.5
108.9
107.7
110.5
109.3
112.0
110.7
113.7
112.2
Mexican
American
MF
118
96
105.3
105.1
4.8
4.9
97.9 99.3
98.1
100.2
98.6
101.7
102.2
104.9
105.1
108.7
108.6
111.2
110.1
111.8
110.7
113.1
Puerto
Rican
MF
41
34
107.3
106.7
6.2
4.7 - -
102.7 104.5
103.4
107.3
106.0
110.1
110.2
112.1 ™ "
Data from Frisancho (1990) and NCHS (1989) )Ll
Table 2
MEANS, STANDARD DEVIATIONS, AND PERCENTILES OF WEIGHT (kg) BY AGE (yn)
FOR MALE AND FEMALE CHILDREN AGES 1-5 YEARS OF DIFFERENT ETHNIC GROUPS
Age
(yn) Race Sex N Mean
11.8
10.9
SD
Percentiles
5 10 15 ?S 50 75 85 90 95
15.0
13.5
1.0-1.9
Black MF
157
134
1.6
1.5
9.6
8.6
9.9
9.1
10.2
9.6
10.7
10.0
11.6
10.8
12.6
11.7
13.4
12.3
14.4
12.8
White MF
508
470
11.8
10.9
1.7
1.4
9.5
8.8
10.0
9.2
10.3
9.5
10.7
9.9
11.6
10.8
12.6
11.8
13.1
124
13.6
128
14.2
13.4
Mexican
American
MF
105
119
11.8
11.0
1.8
1.5
9.5
8.8
9.8
9.3
10.1
9.4
10.8
9.8
11.5
10.9
12.5
12.0
13.1
12.7
13.5
13.2
15.0
13.6
Puerto
Rican
MF
34
33
11.8
11.2
2.0
1.6 -
-
-
10.6
9.8
11.8
11.3
12.7
12.3 - -
-
2.0-2.9
Black MF
142
119
13.5
13.0
1.8
1.8
11.1
10.3
11.3
10.7
11.7
11.2
12.1
11.9
13.4
12.8
14.5
13.9
15.6
14.5
15.9
15.2
16.6
16.2
White MF
513
483
13.6
13.0
1.7
1.6
11.0
10.8
11.6
11.2
12.0
11.6
12.6
12.0
13.6
12.8
14.6
13.9
15.2
14.6
15.5
15.0
16.6
15.9
Mexican
American
MF
HI
121
14.0
13.1
1.7
1.7
11.3
10.8
11.7
11.2
12.1
11.6
13.0
12.0
14.1
12.9
15.0
13.8
15.5
14.7
16.0
15.3
17.0
15.7
Puerto
Rican
MF
35
27
14.7
13.1
2.1
2.0
- - 12.8 13.1
11.9
14.8
128
15.4
14.4
16.0 -
-
3.0-3.9
Black MF
151
128
15.7
15.0
2.4
2.2
12.6
11.8
13.1
12.6
13.4
13.0
14.1
13.7
15.4
14.7
16.8
16.1
17.6
17.2
18.6
17.6
19.8
18.5
White MF
541
509
15.7
15.0
2.0
2.0
12.9
11.8
13.6
12.6
13.9
13.0
14.4
13.6
15.5
14.9
16.8
16.2
17.5
17.1
18.0
17.6
18.9
18.5
Mexican
American
MF
131
97
15.8
15.3
2.3
2.3
12.3 13.0
12.8
13.8
13.1
14.5
13.8
15.4
15.0
16.8
16.8
17.7
17.5
18.3
17.8
19.9
Puerto
Rican
MF
38
40
15.5
15.5
2.0
3.3
- - 13.3
13.0
13.9
13.7
15.5
15.1
16.7
16.5
17.4
17.1 -
-
4.0-4.9
Black MF
151
147
17.9
17.7
2.4
3.0
13.7
13.7
14.7
14.3
15.4
15.0
16.2
16.0
17.9
17.2
19.5
19.2
20.2
20.8
20.8
21.2
21.7
22.4
White MF
547
523
17.7
16.9
2.4
2.2
14.3
13.7
15.1
14.3
15.4
14.6
16.1
15.3
17.5
16.7
18.9
18.3
19.8
19.0
20.5
19.7
21.4
20.9
Mexican
American
MF
118
96
17.7
17.7
2.1
2.7
14.7 14.9
14.9
15.4
15.1
16.2
15.8
17.6
17.6
18.9
19.1
19.5
20.4
20.4
20.6
21.7
Puerto
Rican
MF
41
34
19.2
18.7
4.1
3.6 - -
16.0 16.4
16.1
18.3
17.6
21.1
20.4
22.0 —
:
fS
Data from Frisancho (1990) and NCHS (19b
Table 3
1MEANS, STANDARD DEVIATIONS, AND PERCENTILES OF BODY MASS (w/s1) BY AGE (jn)
FOR MALE AND FEMALE CHILDREN AGES 1-5 YEARS OF DIFFERENT ETHNIC GROUPS
Afe
(y«) Race Sex N Mean SD
Percentiles
5
14.8
14.6
10
15.4
15.2
15 25 50 75 85 90
20.2
19.6
1.0-1.9
Black MF
77
56
17.4
16.8
1.8
1.4
15.8
15.4
16.4
15.8
17.3
16.5
18.2
17.6
19.0
18.2
19.4
18.5
White MF
277
264
17.3
16.8
2.6
1.6
15.3
14.3
15.6
14.9
15.9
15.2
16.4
15.8
17.1
16.7
17.9
17.6
18.6
18.2
18.9
18.8
19.6
19.3
Mexican
American
MF
- - - -
m . . .
-
. .
Puerto
Rican
MF
- -
1.4
1.8
- - -
-
-
-
18.6
18.1
19.0
18.5
2.0-2.9
Black MF
139
118
16.4
16.1
14.5
13.7
14.8
14.1
15.0
14.6
15.4
14.9
16.2
16.1
17.2
17.0
17.9
17.5
White MF
504
479
16.2
16.0
1.3
1.4
14.3
14.1
14.5
14.5
15.0
14.7
15.4
15.1
16.2
15.9
17.0
16.8
17.4
17.3
17.7
17.8
18.2
18.5
Mexican
American
MF
- 16.7
16.3
1.4
1.4
14.6
14.5
15.0
14.8
15.3
15.0
15.5
15.5
16.8
16.2
17.6
17.2
18.2
17.6
18.4
17.8
19.4
18.2
Puerto
Rican
MF
- 16.9
16.5
1.9
1.6 - -
- 15.8
15.4
16.6
16.6
17.6
17.5 - -
-
3.0-3.9
Black MF
151
126
15.9
15.4 B 13.9
13.2
14.6
13.7
14.8
14.1
15.1
14.4
15.7
15.2
16.5
16.2
16.9
16.8
17.2
17.5
18.1
17.9
White MF
540
509
16.0
15.7
1.3
1.3
14.2
13.8
14.5
14.2
14.8
14.5
15.2
14.8
15.8
15.6
16.6
16.4
17.1
17.1
17.5
17.5
18.2
18.0
Mexican
American
MF
- 16.2
16.0
1.6
1.7
14.2 14.5
14.3
14.8
14.5
15.1
15.1
16.0
15.9
16.9
16.8
17.3
17.5
17.8
17.9
18.8
Puerto
Rican
MF
- 15.9
16.1
1.2
3.6
- - 14.6
14.3
14.9
14.6
15.4
15.8
16.1
16.3
17.4
16.8 -
-
4.0-4.9
Black MF
151
147
15.5
15.5 U 13.6
13.3
13.9
13.6
14.3
13.8
14.8
14.3
15.5
15.4
16.3
16.3
16.8
17.1
17.0
17.7
17.4
18.6
White MF
547
519
15.8
15.5
1.4
1.3
14.0
13.7
14.4
13.9
14.6
14.2
14.9
14.6
15.6
15.3
16.4
16.2
16.8
16.7
17.2
17.0
17.8
17.7
Mexican
American
MF
: 15.9
15.9
1.1
1.5
14.1 14.6
14.3
14.8
14.5
15.2
14.8
15.7
15.6
16.6
16.5
16.9
17.3
17.2
18.2
17.8
Puerto
Rican
MF
• 16.5
16.4
2.1
2.2 -
- 14.7 14.9
14.9
15.9
15.9
17.9
17.3
18.9
:
Data from Frisancho (1990) and NCHS (1989)/&
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ft
Technical Paper 2
Anthropometi :e Assessment of Pregnsnt Women
Technicel Paper *2 prepared for the U.S. Department of Agriculture, Food and Nutrition
Service, under Cooperative Agreement #58-3198-1-005, "Review of Nutritional Risk
Criteria for the WIC Program", with the Department of Family and Community Medicine,
University of Arizona, by Gail G. Harrison, PhD, Professor of Family and Community
Medicine, College of Medicine, University of Arizona, Tucson, AZ 85724.
August 6, 1991
■Do
INTRODUCTION
There ere two issues in the snthropometric essessment of women relevsnt to the WIC
progrsm, namely, the classification of women ss under- or overweight on the bssis of non-pregnant
or esrly pregnsncy weight end height, end the essessment of the sdequscy of
weight gain during pregnancy. There is need for attention to both issues, since both
prepregnency weight-f or-height and pregnancy weight gain are strongly related to birth
weight and other pregnancy outcomes. Women who are underweight prior to pregnency
have increesed risk of delivering a low-weight newborn, and women who gain too little
weight during pregnancy are likewise at risk. These risks interact, with the underweight
woman with low weight gain the most at-risk. The optimal outcome of pregnancy is
associated with higher weight gains for women who are initially lean and somewhat lower
gains for those who have high reletive weights before pregnancy. Women who are
markedly overweight prior to pregnancy do best with somewhat lower gains than leaner
women; even so they are at increased risk of inadequate weight gains and have more
variable pregnancy weight gains than leaner women.
This paper reviews current literature and recommendations for categorizing prepregnancy
weight-for-height and for assessing adequacy of pregnancy weight gain. The peper relies
heavily on a recent National Academy of Sciences/Institute of Medicine report on Nutrition
in Pregnancy (IOM, 1990) which provides comprehensive background and recent
recommendations on both issues. The IOM report will no doubt influence obstetric prectice
and public heelth policies for some time to come; the present paper presents s summery of
the relevant sections of that report.
CLASSIFICATION OF RELATIVE WEIGHT ON THE BASIS OF PREPREGNANT STATUS OR
IN EARLY PREGNANCY
Classification of prepregnant relative weight-for-height is based on measured height end
weight either prior to pregnancy or early in pregnancy. If the first contact with a client
occurs past the first trimester, prepregnant weight must be estimated from recall, which
should then be evaluated for plausibility. To assess relative weight, it is necesssry either to
calculate body mass index (BMI) or to compare weight-for-height to a reference standard.
Expression of relative weight as a percentage of a reference populetion mean or median is
the most prevelent method in clinical practice. The calculation is done as follows:
Percentage of reference weight = observed weight X 100
expected or desirable
weight for i given height
The Metropoliten Life Insurance Company (1959) recommendations ere in common clinicel
use. Other possible reference stsndards, less commonly used, include the 1983
Metropoliten Life Insursnce Company tables (which give slightly heevier recommended
weights on averege for age than the earlier edition) and the normative data for White end
Black women from NHANES II. The life insurance company databases were developed to
reflect weights with minimal mortality risk among insured adults and the NHANES data are
normative; none of the available standards reflects optimizstion of any obstetrical outcome.
31
There is no scientific or stetistical basis to recommend any particular reference over
another for the present purpose OOM, 1990).
Body Mass Index (BMI) is a measure of relative weight in more common use in the research
literature. It can be calculated either in metric or English units, as follows (IOM, 1990: 66):
BMI = wt/ht2 « kg/m2 x 100, or lb/in2 x 100
The metric version is standard in the epidemiological and clinical literature. Calculation of
the BMI in English units has the theoretical advantage of being less error-prone in a clinical
setting where initial measures are taken in English units, but comparison with standard
recommendations requires the metric version. A simple conversion chart is available (IOM,
1990) and is included as Appendix A to this paper.
Recent investigators (Abrams and Parker, 1988; Kleinman, 1990; Naeye, 1990) have used
BMI (metric) to describe pregravid weight-for-height, and the recent IOM report (1990)
recommends using a metric BMI of 19.8 - 26.0 as the normal range, pending further
research (see Table 1). This range includes approximately the 25th - 75th percentiles of
prepregnancy weight-for-height of women in the 1980 National Natality Survey (Kleinman,
1990).
Table 1
Categories of Prepregnant Body Mass Index (kg/m2) Used in
Recent Studies of Pregnancy Outcome, and Current Recommendation
Source Cateporv BMI Range
Abrams & Parker, 1988 Average
Moderately
19.2-25.6
Overweight 25.6-28.9
Very
Overweight >28.9
Naeye, 1990 Thin <20
Normal 20-24
Overweight 25-30
Obese >30
Kleinman, 1990 Low <19.8
Moderate 19.8-26.0
High 26.1-29.0
Very High >29.0
IOM, 1990 Underweight <19.8
Normal weight > 19.8-26.0
Overweight > 26.0-29.0
Obese >29.0
2
C?3
Body Mass Index is currently not in common clinical use. A follow-up report to the 1990
NAS/IOM Nutrition in Pregnancy, dealing with practical application of the recommendations, is in
preparation and will include simple conversion and calculation devices for BMI, which will be field
tested over the next year or so.
ASSESSMENT OF THE ADEQUACY OF PREGNANCY WEIGHT GAIN
The major factor affecting the amount of weight gain associated with optimal pregnancy outcome is
prepregnancy weight-for-height. Accordingly, recommendations for weight gain should be adjusted
for an estimate of pregnancy weight-for height. The current recommendations are summarized in
Table 2.
Table 2
Recommended Total Weight Gain Ranges for Pregnant Women*,
by Prepregnancy Body Mass Index (BMI)*
(from IOM, 1990: p. 10)
Recommended Total Gain
Weight-for Height Category kg lb
Low (BMI < 19.8) 12.5-18 28-40
Normal (BMI of 19.8 to 26.0) 11.5-16 25-35
High (BMI > 26.0 to 29.0)* 7-11.5 15-25
' Young adolescents and black women should strive for gains at the upper
end of the recommended range. Short women (< 157 cm or 62 in) should
strive for gains at the lower end of the range.
* BMI is calculated using metric units.
■ The recommended target weight gain for obese women (BMI > 29.0) is at
least 6.0 *g (15 lb).
A number of pregnancy weight gain grids have been developed. Early weight gain charts
(e.g., Thompkins and Wiehl, 1951) were based on normative data from relatively
homogeneous samples of healthy women. More recent charts have usually incorporated
adjustments for prepregnancy weight-for-height and/or larger or different sets of normative
data. The recent IOM report lists no fewer than ten standard grids (IOM, 1990: Table 4-1).
The WIC program itself has, throughout the 1980s, contributed to the public and
professional awareness of the need for standard weight gain charts for nutritional
monitoring during pregnancy. The IOM subcommittee reviewed the weight gain charts
used by WIC programs in 21 states (IOM, 1990: 69). They are most often modifications of
<S?3
Thompkins and Wiehl's (1951) chart, with allowance for prepregnancy weight status. The
particular modifications follow no standard format.
The Institute of Medicine Committee has recommended necessary research to further refine
pregnancy weight gain recommendations, and in the meantime has published provisional
weight gain charts specific to BMI category which are included with this paper as Appendix
B. At this time, these must be regarded as the most current and useable recommendations
for nutrition screening and monitoring of weight gain in pregnancy. There is no substantial
evidence that parity, previous obstetrical history, smoking, use of alcohol or other
substances, physical work, or other variables should affect recommended weight gains
except insofar as they are associated with differential prepregnant weight-for height.
Maternal age and height are of importance only at the very young and very short ends of
the distribution, as noted in the footnotes to Table 2 (i.e., young adolescents should strive
to gain near the top of the recommended range, and women under 62 inches tall to gain
near the bottom of the recommended range). Ethnic background appears to have little
effect except perhaps for Black women, who are recommended to strive for slightly higher
gains than White women within the appropriate range (see Table 2).
Risk of low weight gain (< 15 pounds) is highest among unmarried women. Black and
Hispanic women, cigarette smokers, women with less education, young adolescents, and
obese women. These women should receive increased attention in nutrition monitoring and
counseling during pregnancy to ensure adequate weight gains.
For purposes of monitoring adequacy of weight gain in pregnancy in the WIC clinic setting,
rate of weight gain is more important than total gain. Recommended rates of gain are
given for normal weight, underweight, and overweight women by trimester in Appendix A
and summarized in Table 3:
Table 3
Recommended Rates of Pregnancy Weight Gain by Trimester
Prepregnancy Body Mass 'nde*
19.8-26.0 (Normal Weight)
< 19.8 (Underweight)
26.0-29.0 (Overweight)
Recommended Gain
1.6 kg (3.5 lb) 1st trimester
0.4 kg (1 lb)/week 2nd and 3rd trimesters
2.3 kg (5 lb) 1st trimester
0.5 kg (1 lb)/week 2nd and 3rd trimesters
0.9 (2 lb) 1st trimester
0.3 kg (0.5-0.75 lb)/week 2nd and 3rd trimesters
QL
USE OF OTHER ANTHROPOMETRIC MEASURES (MID-ARM CIRCUMFERENCE,
SKINFOLDS)
While the availability of supplementary anthropometric measures such as skinfold measures
may provide more complete information on body composition, helping to differentiate the
obese from the muscular woman with high weight-for-height, there is little evidence that
the additional information gained is useful for screening or monitoring purposes. Mid-arm
circumference has received some attention as a potential monitoring tool during pregnancy,
particularly for developing country situations in which scales may not be available and
weighing impractical (USAID, 1990). However, weight and height measures offer the best
set of information available when they can be used, and the present paper is based on the
assumption that weight and height will be available in the WIC clinic setting. If there is
significant delay in obtaining weight and height information, and a rough index of risk of
underweight is desired, arm circumference might be used. There is some difficulty at this
point in establishing agreement on the exact mid-arm point to be used in taking the
measurement. There are no relevant data from the U.S. on which to assess the
relationship of arm circumference to pregnancy risk, but data from Asian and Latin
American populations suggest that a prepregnancy or early pregnancy mid-arm
circumference of less than 21-23.5 cm is associated with increased risk of low birth weight
and fetal and infant mortality (USAID, 1990).
SUMMARY
The National Academy of Sciences/Institute of Medicine has recently recommended
assessment of prepregnant weight-for-height be done on the basis of Body Mass Index, the
calculation of which has been simplified by recently published charts. Aids for conversion
to use of this index in clinical practice are being developed. Weight gain recommendations
for pregnancy are specific for pre-pregnancy weight-for-height, with optimal outcomes
associated with higher weight gains for thinner women than for overweight women.
Optimal gains for obese women (BMI >29.0) are not entirely clear, but current
recommendations are for weight gains of at least 6 kg (15 pounds). Rate of weight gain is
potentially of more utility than total pregnancy gain in the WIC clinic setting, and recently
published recommendations, specific for pre-pregnancy weight-for-height, are provided.
While supplementary anthropometric measures such as skinfold thickness and mid-arm
circumference measurements are available, there is little evidence that the additional
information gained is useful for screening or monitoring purposes.
<~?S
REFERENCES
Abrams, B, and J Parker
1988 Overweight and pregnancy complications. International Journal of Obesity
12:293-303.
Institute of Medicine, National Academy of Sciences
1990 Nutrition in Pregnancy. Washington, D.C.: National Academy Press.
Kleinman, JC
1990 Maternal weight gain during pregnancy: Determinants and consequences. NCHS
Working Paper Series No. 33. Hyattsville, MD: NCHS, 24 pp.
Naeye, RL
1990 Maternal body weight and pregnancy outcome. American Journal of Clinical
Nutrition 52:273-279.
Thompkins, WT, and DG Wiehl
1951 Nutritional deficiencies ss a causal factor in toxemia and premature labor.
American Journal of Obstetrics and Gynecology 62:898-919.
U.S. Agency for international Development
1990 Summary statement on "Maternal Anthropometry for Prediction of Pregnancy
Outcomes", from a conference of the same title, April 23-25, 1990. Submitted
for publication to the Bulletin of the World Health Organization.
6
Appendix A
Table for Estimating Body Mass Index (Metric) by Using Either
Metric or English Measurements of Prepregnancy Weight and Height;
BMI < 19.8 ■ low; BMI 26.1 - 29.0 ■ high; BMI > 29.0 = obesity
(see shaded area above heavy line).
from: IOM/NAS, 1990
o?7
Weight Height, in. (and cm)
lb kg
35.9 56.7 57.5 58.3 59.1 59.8 60.6 61.4 62.2 63.0 63.8 64.6 65.4 66.1 66.9 67.7
(I42)(I44)(I46)(I48X|50XI52)(I54X156X158X160)(I62)(IM)(I66)(168X170X17:
68.5 69.3 70.1 70.9 71.7 72.4 73.2 74.0
H174H176) (178X180) (182X184X1861 (188)
128.9 28.3
|28.6 28.0
28.3 27.7
220 100 49.6 48 2 46.9 45.7
218 99 49.1 47.7 46.4 45-2
216 98 48.6 473 46.0 44.7
213 97 48.1 46.8 45.5 44.3
211 96 47.6 46.3 45.0 43.8
209 95 47.1 453 44.6 43.4
207 94 46.6 45.3 44.1 4Z9
205 93 46.1 44.8 43.6 4X5
202 92 45.6 44.4 43.2 42.0
200 91 43.1 43.9 4Z7 413
198 90 44.6 43.4 4X2 41.1
196 89 44.1 •■'..9 41.8-40.6
194 88 43.6 42.4 4L3 402
191 87 43.1 42.0 40.8 39.7
189 86 42.7 415 403 39J
187 85 <T2 41.0-39.9* 383
185 84 4X7 403 39.4:383
183 83 413 40.0 38.9 77.9
180 82 40.7 39.5 38-5-37.4
178 81 402 39.1 HJTVJ
176 80 39.7 3X6 373 363
174 79 39.2 3X1 37.1 £36.1
172 78 38.7 37.6 363 35-6
169 77 312 37.1 36.1 252
167 76 37.7 36.7 3X7;34.7
165 751372-36.2 35 2:342
163 74 36.7 35.7 34.7:33.8
161 73 362 353 342.333
158 72 35.7.34.7.33.8 32.9
156 71 352 343~3X3 32.4
154 70J4.7JMLSA.22i>
44.4 433 422
44.0 42.8 41.7
43.6 42.4 41.3
43.1 42.0 40.9
42.7 41.6 403
422 41.1 40.1
41.8 40.7 39.6
413 403 392
40.9 39.8 38.8
40.4 39.4 38.4
40.0 39.0 37.9
39.6 383 373
39.1 38.1 37.1
38.7 37.7 36.7
382 372 363
373'363 353
373 36.4 35.4
36.9 35.9 35.0
.36.4 353 34.6
36.0 35.1 342
35.6 34.6 33.7
35.1 342 333
34.7 33.8 32.9
342 333 323
333 32.9 32.0
333 323 31.6
32.9 32.0 3L2
32.4 31.6 303
3X0 3L2-30.4
313 30.729.9
31.1 J0J.293
41.1 40.1 39.1
40.7 39.7 38.7
403 393 383
39.9 38.9 37.9
39.4 383 373
39.0 38.1 37.1
38.6 37.7 36.7
382 373 363
37.8 36.9 35.9
37.4 363 353
37.0 36.1 352
36.6 33.7 343
362 353 34.4
35.7 34.9 34.0
353 34.4 333
34.9 34.0 332
343 333 323
34.1 332 3X4
33.7 3X8 3X0
333 3X4 313
3X9 3X0 313
323 31.6 30.9
3X1 312 303
31.6 303 30.1
312 30.4
303 30.0
30.4 29.6)28.9
30.0 ,&2j28.5
283 28.1
128.4 27.7
283 28.0 273
29.7
38.1 372 363 35.4
37.7 363 35.9 35.1
373 36.4 353 34.7
37.0 36.1 353 34.4
36.6 35.7 343 34.0
362 353 343 33.7
353 34.9 34.1 333
35.4 343 33.7 33.0
35.1 342 33.4 3X6
34.7 333 33.0 222.
343 333 3X7 31.9
33.9 33.1 323 313
333 3X7/3X9 31.2
332 323 3L6 30.8
32.8.3X0 313 303
32.4 3131303 30.1
3X0 3LT303 "293
31.6'30.9 30.1.29-
3L2303..-29J
30.9 30.1 29.4128.7
303 29.7 |35!o 28.3
30.1 29.4 128.7 28.0
29.7129.0 28.3 27.6
28.6 27.9 273
29.0 283 27.6 26.9
28.6 27.9 272 26.6
282 273 26.9
273 27.1 263
27.4 263 26.1125.5
27.1 26.4 (253 25.2
26.7126.0 25.4 24.8
34.6 33.8
343 333
33.9 33.1
33.6 3X8
332 32.4
3X9 3X1
3X5 313
3X2 31.4
313) 31.1
313 303
31.1 30.4
30.8 30.1
30.4 29.7
30.1 29.41
293
29.4|28.7
28.4
.7 28.1
28.4 27.7
28.0 27.4
27.7 27.0
273 26.7
25.i
31.6 30.9
312 30.6
30.9 302
30.6 29.9
303 29.61
30.0
29.7129.0
28.7
.0 28.4
28.7 28.1
28.4 27.8
28.1 273
27.8 272
27.5 26.9
27.1 26.5
29.5
28.0
27.7
27.5
27.2
27.4
27.2
26.9
26.6
29
4128
26.
25.9
J2S.6
II5.9 25.3
J25.6 25.0
25.2 24.7
24.9 24.4
24.6 21.1
243 233
24.0 23.5
23.7 23.1
23.4 22.8
23.0 22.5
22.7 222
22.4 21.9
22.1 21.6
26.0
25.7
25.4
25.1
24.8
24.5
24.2
23.8
23.5
23.2
22.9
22.6
2X3
26.0
|23.7
25.4
25.1
24.8
24.5
24.2
23.9
23.6
23.3
23.0
22.7
22.4
22.2
21.9
26.9 26.3_
26.6 [26.0
26.3 |25.7
126.0 25.5
|25.7 25.2
25.4 24.9
25.1 24.6
24.9 24.3
24.6 24.0
24.3 23.8
24.0 23.5
23.7 23.2
23.4
23.1
22.8
22.5
22.9
22.6
22.4
22.1
22.3 21.8
22.0 21.5
21.7 21.2
22.0 21.6
21.7 21.3
21.4 21.0
21.1 20.7
21.4
21.1
20.8
20.5
20.2
20.9
20.7
20.4
20.1
19.8
152 691342 333 JX4-313 30.729.9 SJ,128.4 27.6 27.0 263125.7 25.0 24.4 23.9 233 22.8 22.3 21.8 21.3 20.8 20.4 19.9119.5
ISO 68 33.7 3X8 3JS31.0 302T9JJ2T7 27.9 272 26.6 25.9 25.3 24.7 24.1 233 23.0 22.5 22.0 21.5 21.0 20.5 20.1 |19.7 19.2
147 67:333 3X3 31.4^30.6 2931293 283 273 263 26.2 J25.S 24.9 24.3 23.7 232 22.6 22.1 21.6 21.1 20.7 20.2 198 19.4 19.0
145 66 3X7 313-3L0I30.1 293128.6 273 27.1 26.4125.8 25.1 24.5 24.0 23.4 22.8 22.3 21.8 21.3 20.8 20.4 19.9 |19.5 19.1 18.7
143 65 3X2 313 303 29.7 28.9 28.1 27.4 26.7 126.0 25.4 243 243 23.6 23.0 22.5 22.0 21.5 21.0 20.5 20.1 119.6 19.2 18.8 18.4
141 64 31.7 30.9 30.0 29.2128.4 27.7 27.0 25.6 25.0 24.4 23.8 23.2 22.7 22.1 21.6 21.1 20.7 20.2 19.8 19.3 18.9 18.5 18.1
139 63.313 -30143931283 28.0 273 26.6 j 25.9 21.2 24.6 24.0 23.4 22.9 223 21.8 21.3 20.8 20.3 19.9 |19.4 19.0 18.6 18.2 17.8
136 62 30.7:29.9 29.1128.3 27.6 263 26.1 |253 24.8 242 23.6 23.1 223 22.0 21.5 21.0 20.5 20.0 \wl 19.1 18.7 183 17.9 173
134 61 303 JLU28.6 27.8 27.1 26.41257 23.1 24.4 23.8 232 22.7 22.1 21.6 21.1 20.6 20.1 119.7 193 183 18.4 18.0 17.6 17.3
132 60 293128.9 28.1 27.4 26.7|26.0 25.3 24.7 24.0 23.4 22.9 223 21.8 213 20.8 20.3 19.8 19.4 189 183 18.1 17.7 173 17.0
130 59 293 128.5 27.7 26.9 26.21253 24.9 24.2 23.6 23.0 223 21.9 21.4 20.9 20.4 199 fi57 19.0 18.6 18.2 17.8 17.4 17.1 16.7
128 58 283 28.0 273 2631253 25.1 24.5 23.8 233 22.7 22.1 21.6 21.0 20.5 20.1 |19.6 193 1X7 1X3 17.9 173 17.1 163 16.4
125 57 283 27.5 26.7 26.0 25.3 24.7 24.0 23.4 22.8 22.3 21.7 213 20.7 202 \wJ 193 18.8 18.4 18.0 17.6 173 16.8 163 16.1
123 56 27.8 27.0 263125.6 24.9 24.2 23.6 23.0 22.4 21.9 21.3 20.8 20.3 198 19.4 18.9 18.3 18.1 17.7 173 16.9 16.5 162 15.8
121 55 273 263125.8 23.1 24.4 23.8 232 2X6 22.0 21.5 21.0 20.4 20 0 \w~ 19.0 18.6 182 173 17.4 17.0 16.6 163 15.9 15.6
119 54 26.8 26.0 25.3 24.7 24.0 23.4 22.8 22.2 21.6 21.1 20.6 20.1119.6 19.1 18.7 1X3 17.8 17.4 17.0 16.7 16.3 15.9 15.6 13.3
117 33 263125.6 24.9 243 23.6 2X9 223 21.8 21.2 20.7 202(197 192 18.8 183 17.9 173 17.1 16.7 16.4 16.0 15.7 153 15.0
114 52 25.8 25.1 24.4 23.7 23.1 22.5 21.9 21.4 20.8 20.3 19.81193 1X9 18.4 18.0 17.6 173 16.8 16.4 16.0 15.7 15.4 15.0 14.7
112 51 253 24.6 23.9 23.3 22.7 22.1 21.5 21.0 20.4 19.9 119.4 19.0 183 18.1 17.6 172 16.8 163 16.1 15.7 15.4 15.1 14.7 144
no SO 24.8 24.1 23.5 2X8 222 21.6 21.1 20.5 2001193 19.1 18.6 18.1 17.7 173 16.9 163 16.1 153 15.4 1S.I 14.8 143 14.1
108 49 24.3 23.6 23.0 22.4 21.8 212 20.7 20.1 119.6 19.1 18.7 18.2 17.8 17.4 17.0 16.6 162 1S3 15.5 15.1 14.8 14.5 14.2 13.9
106 48 23.8 23.1 223 21.9 21.3 20.8 20.2 jlT 192 183 183 17.8 17.4 17.0 16.6 162 15.9 153 15.1 14.8 14.5 14.2 13.9 13.6
103 47 23.3 2X7 22.0 21.5 20° 20.3 19.8 193 18.8 1X4 17.9 173 17.1 16.7 163 15.9 153 153 143 143 142 13.9 13.6 13.3
101 46 22.8 22.2 21.6 21.0 20 i 19.9 (1X4 18.9 18.4 18.0 173 17.1 16.7 163 15.9 153 152 14.9 14.5 142 13.9 13.6 133 13.0
99 43 22.3 21.7 21.1 20.5 20 01193 19.0 183 18.0 17.6 17.1 16.7 163 15.9 15.6 152 14.9 143 142 13.9 13.6 13.3 13.0 12.7
97 44 21.8 21.2 20.6 20 1119.6 19.0 1X6 18.1 17.6 173 16.8 16.4 16.0 15.6 152 14.9 143 14.2 13.9 13.6 133 13.0 1X7 12.4
95 43 21.3 20.7 20.2 (193 19.1 18.6 18.1 17.7 173 163 16.4 16.0 15.6 152 14.9 143 143 13.9 13.6 133 13.0 12.7 1X4 122
92 42 20.8 20.3)19.7 192 18.7 183 17.7 173 16.8 16.4 16.0 15.6 152 14.9 14.5 142 13.9 13.6 133 13.0 12.7 12.4 12.1 11.9
90 41 20.3 19 81193 18.7 182 17.7 173 16.8 16.4 16.0 15.6 153 14.9 143 143 13.9 133 132 1X9 12.7 12.4 12.1 11.9 11.6
88 40 19.8 fl93 183 183 17.8 173 16.9 16.4 16.0 15.6 152 14.9 14.5 14.2 13.8 133 132 12.9 1X6 1X3 12.1 11.8 11.6 113
' BMI (metric) - (kf/m2) x 100 : BMI (English) - (lb/in.2) x 100.
BMI (metric) x 0.142 - BMI (English): BMI (English) x 7 - BMI (metric).
Appendix B
Provisional Weight Gain Charts by Prepregnancy Body Mass index
(BMI)
from: IOM/NAS. 1990
Sc)
A. For Normal Weight Women with BMi
Of 19.8 to 26.0 (Metric)8
50
40
1st 2nd 3rd
I 20
10 -
TARGET: 15.5 TO 16 kg (25 to 35 16) il 40 wkt
with ■ giin of 0 4 kg (1 lo) / •*
during trimtmr 2 MS 3
./
/
/
/
/
X /
/
tU.
20
15
10
4
O
0 5 10 15 20 25 30 35 40 45
Week of Gesution
'Assumes a 1.6-kg (3.5-lb) gain in first trimester and the remaining gain at
a rate of 0.44 kg (0.97 lb) per week.
*Assumes a 13-kg (5-lb) gain in first trimester and the remaining gain at a
rate of 0.49 kg (1.07 lb) per week.
'Assumes a 0.9-kg (2-lb) gain in first trimester and the remaining gain at a
rate of 03 kg (067 lb) per week.
30
O
B. For Underweight Women with BMI
Less Than 19.8 (Metric)"
1st 2nd 3rd
50
40 -
30 -
I 20
10 -
TARGET: 12.5 to 18 kg (28 «o *0 to) at 40 ~*»
with a gam of 0.5 kg (1 10) / w*
during trimtmr 2 ana 3.
•^
*
/
/J
-
/
/
/
/
/
/
/
•'* ■ ' ' 1 ' 1 ' 1 L_
- 20
15
caO
10 |
- 5
0 5 10 15 20 25 30 35 40 45
Week ol Gestation
C. For Overweight Women with BMI
of > 26.0 to 29.0 (Metric)0
i
1st 2nd
50r-»
3rd
40
30
20
10
TAA3ET: 7 to 11JS kg (15 to 25 to) at 40 «
wNhtgainofa3hg|&Sto0.73tt>)/«*
during trimtstof 2 and 3.
/A
/
/
s
- i: ■ i ■ ■
20
15 5
3
10
0 5 10 15 20 25 30 35 40 45
Week of Gestation
31
Technical Paper 3
Overweight and Obesity in Pregnancy
Technical Paper #3 prepared for the U.S. Department of Agriculture, Food and Nutrition
Service, under Cooperative Agreement #58-3198-1-005, "Review of the Nutritional Risk
Criteria for the WIC Program", with the Department of Family and Community Medicine,
University of Arizona, by April H. Dean, MS, RD, and Gail G. Harrison, PhD. Ms. Dean is
Research Associate and a doctoral candidate in Nutritional Sciences; Dr. Harrison is
Professor of Family and Community Medicine, College of Medicine, University of Arizona,
Tucson, AZ 857».
August 6, 1991
33
INTRODUCTION
Overweight and obesity are highly prevalent among U.S. adults; therefore the implications
of these conditions for nutritional risk in pregnancy are of interest in targeting of the WIC
program, designed to reach low-income and medically/nutritionally at-risk pregnant women,
postpartum women, infants and children. This technical paper will review the available
information in the literature and current recommendations to address the following issues:
- What are the risks of overweight and obesity in pregnancy?
How should overweight and obesity be defined for pregnant women?
- What is the optimal weight gain in pregnancy for the overweight and obese
woman?
Nutritional management of obesity during pregnancy.
DEFINITIONS AND MEASUREMENT
There are a variety of definitions for overweight end obesity available in the literature and in
clinical use. Strictly speaking, overweight refers to body weight relative to height which is
in excess of that determined to be optimal for a particular set of health outcomes or
mortality risk; obesity refers to an excess of body fat, again relative to a standard range
determined to be optimal for a defined outcome or risk. Measurement of body fat is much
less frequently accomplished in either survey or clinical contexts than are height and weight
measures, although skinfold thickness measures are available for large enough reference
populations to use them as clinical criteria.
In common clinical and epidemiologic use, relative weight is used as a continuous variable
with the term "overweight" used to refer to milder and moderate degrees of excess weight
for height and "obesity" used to refer to extremely high weight for height. This convention
is probably reasonably valid, since the correlation of relative weight with body fatness is
sufficiently high particularly at the extreme ends of the continuum to justify the assumption
of excess body fat in the severely overweight individual.
Measures of relative weight in common use include weight as a percent of a standard
weight for a given range of height, derived from a reference population, and body mass
index (BMI), which is calculated as weight in kilograms divided by height in meters with
height raised to an exponent which is variably between 1.5 end 2.0. The calculation is
designed to minimize or remove the effect of the fact that height and weight are highly
correlated with one another. The Quetelet Index (kg/m2) is the most commonly used BMI,
while the National Center for Health Statistics uses a BMI calculated as kg/m ,J for women.
Evaluation of obesity for the pre-gravid woman is complicated by the fact that none of the
available standards are designed to reflect levels of relative weight or fatness at which the
risk for complications of pregnancy is elevated. Rather, they are either normative data
based on the distribution of weight-for-height or fatness in the U.S. population (e.g.,
NHANES data), or they are developed to reflect lowest mortality risk among insured adults
(i.e.. Metropolitan Life Insurance Company standards).
The available literature has not used consistent standards for defining obesity or overweight
in pregnant women (Garbaciak et al., 1980; Gross et al., 1980; Abrams and Parker, 1988;
1
33
Naeye, 1990). The least interpretable index is used by Gross et al. (1980) of "maximum
pregnancy weight" since it does not take into account prepregnant weight vs. weight gain
during pregnancy. The two most recent comprehensive studies of pregnancy risk and
relative weight have used BMI (Quetelet's Index) criteria (Naeye, 1990 and Abrams and
Parker, 1988) with relatively arbitrary but fairly congruent cutoff points.
A recent Institute of Medicine report on Nutrition and Pregnancy (IOM, 199) provides the
current recommended criterion for classification of overweight and obesity. Obesity is
defined, using the Quetelet method, as a BMI (kg/m3) greater than 29.0 while overweight is
defined as BMI between 26.0 and 29.0. For comparative purposes, weight-for-height at
120 percent of the Metropolitan Life Insurance population corresponds to a BMI Index of
25.6, and 135 percent of standard corresponds to 28.9.
PREVALENCE OF OVERWEIGHT AND OBESITY AMONG WOMEN OF CHILDBEARING AGE
Estimates of the prevalence of overweight and/or obesity vary with the definitional criteria
used. If weight-for-height at least 120 percent of life insurance reference tables is used as
a criterion for obesity (e.g., Garbaciak et at., 1985), then nearly 20 percent of reproductive-aged
women in the U.S. can be considered overweight (Varner, 1985). Using BMI ;>85th
percentile of national reference data for women in their 20s to define overweight and BMI
2:95th percentile to define severe overweight, 27 percent of women in the U.S. are
overweight and approximately 11 percent are severely overweight (Najjar, 1987).
All available data indicate that the prevalence of overweight and obesity among women in
developed countries is inversely releted to income and social class (Stunkard, 1988;
Goldblatt et al., 1965). Thus we mey expect the prevalence of these conditions to be
higher among WIC-eligible women than among women of comparable age in the general
population. Stockbauer (1987) reported that 18.1 percent of the Missouri WIC prenatal
participants had prepregnancy weights greater than or equal to 20 percent over standard
weight for height, compared to 13.5 percent in non-WIC women in the same state.
Overweight is also non-randomly distributed in the population with respect to age,
education, ethnic group, and region. Deta from the NHANES II survey and the Hispanic
Health and Nutrition Survey (HHNS, 1982-84) show that among the ethnic groups studied
Black women had the high highest prevalence of overweight, followed by Mexican-
American and Puerto Rican women; the lowest prevalence was seen in non-Hispanic White
women, followed by Cuban women (Life Sciences Research Office, 1989). Mean BMI was
higher in both Black and White women with lower educational levels than among more
educated women (LSRO, 1989). Gillum (1987), also analyzing NHANES II data, reported
that rural and southern Black women aged 25-74 yeers were more overweight than Black
women residing in urban arees and in the northern and western regions. The prevalence of
obesity and overweight increases with increasing age among women during their
childbearing years (Naeye, 1990).
RISKS OF OBESITY IN PREGNANCY
The physiological stress of obesity is manifested in increased rates of hypertension (NIH,
1979), impaired respiratory function (Ray, 1983), gallbladder disease (Bray, 1985) and
diabetes (Topeller et al., 1982). It is not surprising that the added metabolic demands of
pregnancy may predispose to various forms of increased risk. Some of the reported
o?<-/
complications of obesity in pregnancy include higher rates of preeclampsia, hypertension,
diabetes mellitus, thromboembolic disease, urinary tract infections, Caesarean delivery,
therapeutic induction of labor, prolonged second stage of labor, prolonged gestation (>42
weeks), and perinatal mortality. Schramm (1981) reported that overweight (> 120 percent
ideal weight for height) women in Missouri had increased essential and pregnancy-induced
hypertension rates, risk of diabetes, abnormalities of labor, twins, and fetal deaths.
Abrams and Parker (1988) have recently summarized results from their own work and from
two other large investigations to determine the relative risks of certain complications of
pregnancy due to moderate and severe overweight. They concluded that even moderately
overweight women were at higher risk than average for diabetes, pregnancy-induced
hypertension, and primary Caesarean deliveries, although severely overweight women bear
still higher risks. Very overweight women were 6.5 times more likely to manifest diabetes
during pregnancy and 1.9 times as likely to develop pregnancy-induced hypertension than
women of average weight. Very overweight women experienced increased risk of 85
percent for perinatal mortality, 60 percent for Caesarean delivery and 42 percent for urinary
tract infections; the relative risk for anemia for very overweight women was decreased
(0.67) compared to women of average weight.
Early studies (Douglas and Scadron, 1951; Fisher and Frey, 1958) indicated that despite
higher risk of complications during pregnancy, perinatal mortality did not increase with
maternal obesity. More recent and comprehensive studies, however, contradict this
conclusion and indicate substantially increased mortality risk. A report based on data from
the National Natality Survey (NNS) (Taffel, 1986) found that fetal death rates were highest
among the heaviest women (>72 kg). Garbaciak et al. (1985) investigated the effect of
obesity on pregnancy outcome in 9,667 patients, and found significant increases in
perinatal mortality among obese and morbidly obese women with antenatal complications;
among obese women with and without complications there were increased rates of primary
Caesarean delivery and increased mean birth weights compared to nonobese women.
Rahaman et al. (1990) reported similar findings in a study examining outcome of pregnancy
in 300 obese (BMI > 30) women. Perinatal loss was ten times greater among the obese
mothers than among nonobese controls, with diabetes, pre-eclampsia and advanced
maternal age largely contributing to the difference. These authors also concluded that the
obese woman without other risk factors or complications of pregnancy bears no elevation
of risk in terms of fetal outcome.
A recent study provides some evidence of a relationship between maternal obesity and
decreased viability of infants born pre-term. Lucas and colleagues (1988) reported that
maternal fatness was second in importance only to length of gestation in predicting he
death of infants bom preterm. They also found that premature infants had decreasing birth
weight for gestational age with increasing maternal fatness, a finding which is somewhat
surprising given the well-established relationship between maternal fatness and increased
birth weight and risk of macrosomia in term infants (Calandra et al., 1981).
Naeye (1990) examined 56,857 pregnancies from the National Collaborative Perinatal
Study and concluded that perinatal mortality rates progressively increased with increases in
maternal pregravid relative body weight. Much of the increase was due to preterm
deliveries between 24 and 30 weeks gestation, which were often caused by acute
chorioamnionitis. A greater frequency of dizygotic twins was observed with increasing
3D
maternal relative weight, which contributed somewhat to the increase in preterm deliveries.
This study confirmed the findings of Lucas et al. (1988) that perinatal mortality rates for
pre-term infants born to obese mothers progressively increase with increasing maternal
preconceptual weight. The mortality rate for infants born to obese mothers was 121/1000
births compared to infants of thin mothers, who experienced the lowest mortality rate of
37/1000. Major congenital malformations also increased with relative maternal body
weight, and these effects persisted after several risk factors were taken into consideration
analytically. This same analysis identified a correlation between perinatal mortality risk and
low socioeconomic status, which disappeared when relative maternal body weight and
other risk factors such as cigarette smoking were taken into account. An observed
correlation between perinatal mortality and ethnicity (Bleck women higher than White) also
nearly disappeared when these risk factors were taken into account.
NUTRITIONAL MANAGEMENT OF PREGNANCY IN THE OBESE WOMAN: WEIGHT GAIN
AND DIETARY RISK
Several investigators (Abrams and Parker, 1988; Garbaciak et al., 1985; Johnson et al.,
1987) have pointed out that because of the greeter risk of complications, adequate prenatal
care including early screening and treatment for diabetes and hypertension is particularly
important for overweight women. The overweight pregnant woman should also routinely
be screened for urinary tract infections, since she carries a 9 percent greater risk than the
average woman. Accurate establishment of gestational age is more difficult in the obese
woman but is particularly important because of increased risk of ineffective labor (Johnson
etal., 1987).
Averege birth weight tends to be elevated in the offspring of obese women (Rossner and
Ohlin, 1990;garbaciak,1985; Calandra et al., 1981; Harrison et al., 1981) and the risk of
macrosomia (infant birth weight > 4000 g) increases, increasing the risk for Caesarean
delivery and/or birth trauma. However, one recent study (Rossner and Ohlin, 1990)
concluded that increasing birth weight with metemel relative weight only held true up to a
maternal BMI of 24 kg/m3. At higher relative weights, birth weight did not increase with
maternal weight.
The risk of low weight gain and even lack of weight gain is elevated in severely obese
women, but the relative effect on newborn size is buffered compared to nonobese women
(Harrison et al., 1981). An analysis of the 1980 NNS data (Kleinman, 1990) showed mean
gestational weight gain decreased as maternal prepregnancy BMI increased, and the
variation in gain increased. More than 10 percent of very overweight women lost weight
during pregnancy, and approximately one-third had "low" weight gain of 15 pounds or less,
a four-fold measure over women with normal prepregnancy BMI.
Dietary patterns and nutritional intake in obese and overweight pregnant women require
particular attention, and may have been generally neglected on an invalid assumption that
the overweight are adequately nourished. Studies of nonpregnant overweight women
indicate a prevalence of dieting of more than 50 percent (Forman et al., 1986); a high risk
for dieting among overweight pregnant women is reflected in elevated risk for low or even
negative weight gains during pregnancy among the obese (Harrison et al., 1981). Pregnant
women who smoke, like nonpregnant adults who smoke, have been shown to have less
nutrient dense diets than nonsmokers (Asronson end Macnee, 1989); thus the overweight
Jip
pregnant woman who smokes may represent a particularly at-risk situation in terms of
nutritional inadequacy.
There is some evidence (Borberg et al., 1980) that non-diabetic, obese pregnant women
receiving dietary advice from a dietitian were able to limit the increase in insulin
concentrations of late pregnancy when compared with obese pregnant women not
receiving dietary information.
OPTIMAL AND RECOMMENDED WEIGHT GAINS FOR OBESE WOMEN
Naeye (1979) reported improved perinatal outcome in moderately obese individuals (> 135
percent ideal body weight) who limited gestational weight gain to 16 pounds. Winick
(1986), in contrast, recommended 20- to 27-pound weight gains for overweight women.
Ratner et al. (1991) have recently examined the effects of varying pregnancy weight gain
in women with prepregnancy weight greater than 160 percent of ideal, all of whom
received nutrition counseling in pregnancy. They found the incidence of primary
Caesarean delivery to be greater for obese women who gained more than 24 pounds, and
concluded that a gestational weight gain of only 10 pounds in the morbidly obese
minimized maternal risks without increasing ketonuria or intrauterine growth retardation.
The recent Institute of Medicine report (IOM, 1990) recommends a minimum gain of 6
kilograms for obese women.
SUMMARY
The incidence of obesity and related health problems is increasing in the United States.
This is particularly a problem among women and minority populations. Women of low
socioeconomic status and lower educational levels are more likely to be obese than those
of higher socioeconomic and education levels.
Obesity can be a serious health risk during pregnancy. It is associated with higher rates of
preeclampsia, hypertension, diabetes mellitus, urinary tract infection, acute
chorioamnionitis, dizygotic twins, major malformations, and Caesarean delivery. Infants
born to obese women are more likely to be macrosomic, which increases their likelihood of
experiencing birth trauma. Several researchers report increases in perinatal mortality.
Preterm infants born to obese mothers often have small birth weights for their gestational
ages and are less likely to survive. Fetal death rate is highest among the heaviest women.
The risk associated with obesity increases progressively from women who are very thin
pregravid to those who are obese. There appears to be no clear threshold, and thus cutoff
points of weight-for-height or BMI are arbitrary classifications in this respect.
Adequate and early prenatal cere which includes early screening and treatment for diabetes
and hypertension are especially important for obese women. Some evidence suggests that
education concerning an appropriate, balanced diet during pregnancy can positively affect
some of the risk factors of this condition.
Weight gain during pregnancy is generally lower, and is more variable for obese than
normal-weight women. Researchers disagree about the appropriate amount of weight an
obese woman should gain during pregnancy. While there is some disagreement about the
optimal pregnancy weight gain for the obese woman, the current recommendation from a
37
recent Institute of Medicine study is to encourage weight gsins of at teest 6 kg (15
pounds).
Little is known sbout the nutrient intskes of obese women in their childbesring yeers.
There is s greet need for further reseerch defining the role of food/nutrient inteke in
modifying the complicstions of pregnsncy observed in overweight women, end in
understending the dietery behavior of overweight and obese women during pregnancy.
6
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1988 Overweight and pregnancy complications. International Journal of Obesity
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Bernstein, RA. EE Giefer, JJ Vieera, LH Werner, and AA Rimm
1977 Gallbladder disease: Observations in Framingham study. Journal of Chronic
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Borberg, C, MDG Gillmer, EJ Brunner, PJ Gunn, NW Oakley, and RW Beard
1980 Obesity in pregnancy: The effect of dietary advice. Diabetes Care 3(3):476-
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Bray, GA .
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Fisher, JJ, and I Frey
1958 Pregnancy and parturition in the obese patient. Obstetrics and Gynecology
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Forman, MR, FL Trowbridge, EM Gentry, JS Marks, and GC Hogelin
1986 Overweight adults in the United States: The behavioral risk factor surveys.
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1985 Maternal weight and pregnancy complications. American Journal of Obstetrics
and Gynecology 152:238-245.
1987 Overweight and obesity in Black women: A review of published data from the
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Gross, T, RJ Sokol, and KC King
1980 Obesity in pregnancy: Risks and outcome. Obstetrics and Gynecology
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<2 ci
Harrison, GG, JN Udall, and G Morrow
1980 Maternal obesity, weight gain in pregnancy, and infant birth weight. American
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1987 Maternal obesity and pregnancy. Surgery, Gynecology and Obstetrics
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Kleinman, JC
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1990 Macrosomia: Influence of maternal overweight among a low-income
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1988 Maternal fatness and viability of preterm infants. British Medical Journal
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1990 Maternal body weight and pregnancy outcome. American Journal of Clinical
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1990 Fetal outcome among obese parturients. International Journal of Gynecology
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1991 Effects of gestational weight gain in morbidly obese women. I. Maternal
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1983 Effect of obesity on respiratory function. American Review of Respiratory
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Rossner, S, and A Ohlin
1990 Maternal body weight and relation to birth weight. Acta Obstetricia Et
Gynecologica Scandinavia 69:475-478.
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Public Health Service. Washington, D.C.: U.S. Government Printing Office.
Toeller, M, FA Gries, and K Dannehl
1982 Natural history of glucose intolerance in obesity: A ten year observation.
International Journal of Obesity 6 (Suppl 1): 145-149.
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Winick, M
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MQ
Technictl Paper 4
Overweight and Obesity in infants and Children
Technical Paper #4 prepared for the U.S. Department of Agriculture under Cooperative
Agreement #58-3198-1-005, "Review of the Nutritional Risk Criteria for the WIC Program",
with the Department of Family and Community Medicine, University of Arizona, Tucson,
AZ 85724 by April H. Dean, MS, RD, Research Associate. Ms. Dean is a doctoral
candidate in the program of Nutritional Sciences, University of Arizona.
August 6, 1991
/'<B
INTRODUCTION
The purpose of this technical paper is to review current published information and scientific
opinion on several issues related to obesity in early childhood, namely trends in prevalence,
consequences and health risks, etiology, and prevention and management strategies.
TRENDS IN PREVALENCE OF OBESITY IN CHILDREN
There is evidence that the problem of pediatric obesity in the United States is increasing at
an alarming rate. Depending on the criteria used to define obesity, which at best are
arbitrary in children, as many as 25% of children are affected. Gortmaker et al. (1987)
have presented convincing evidence for the increasing prevalence. Defining obesity as
triceps skinfold thickness greater than the 85th percentile and severe obesity as triceps
skinfold greater than the 95th percentile of reference data from the National Health
Examination Survey Cycles II and III (1963, 1965-1970), they compared information
collected from the NHANES I (1970-1973) and NHANES II (1975-1980). Over the 17-year
period, the prevalence of obesity increased by 54% in children aged six to eleven years and
by 39% in adolescents. The prevalence of severe obesity increased by 95% in children
and 64% in adolescents. Increased prevalence characterized all socioeconomic categories
and occurred in Blacks as well as Whites, although obesity was less prevalent among Black
children than among Whites throughout the time period.
Analysis of the Hispanic Health and Nutrition Survey (HHANES) data reveals that the
increased risk for obesity among Mexican-Americans begins early. Mexican-American
children are heavier than non-Hispanic White and Black children at all ages (Martorell et al.,
1989). A tendency toward greater relative deposition of fat on the trunk in Mexican-
American compared to non-Hispanic White children has been documented in children as
young as one year of age (Kautz and Harrison, 1981). Overweight in Native American
children has also increased dramatically in the last several years (Sugarman et al., 1990).
CONSEQUENCES OP OBESITY POR CHILDREN
Metabolic Changes
While the health risks associated with obesity in adults are well documented and include
noninsulin dependent diabetes mellitus (Kissebah et al., 1989; Lew and Garfinkel, 1979),
several types of cancer (Lew and Garfinkel, 1979), hypertension, hypercholesterolemia, and
hypertriglyceridemia (NIH, 1985), such risks are not as extensively documented for
children. Severe obesity in both groups is associated with increased risk of atherosclerotic
heart disease (Keys, 1980). Rosenbaum and Leibel (1989) have reported that obese
children manifest many of the same disturbances as obese adults, including
hyperinsulinism, hyperlipidemia, and hypertension (Court et al., 1974; Rosenbaum and
Leibel, 1988). Obese children are generally tall for age, mature early (Wolff, 1955) and
may have advanced bone age (Garn, 1976). Although there are conflicting reports (Cooper
et al., 1990), obese children have been found to be less physically fit than the nonobese
(Zanconato et al., 1989). They may have increased risk of respiratory problems
(Sommerville et al., 1984).
<4<t
In an attempt to identify children at greetest risk for future development of cardiovascular
disease, a recent report of an expert psnel on blood cholesterol levels in children and
adolescents by the National Cholesterol Education Program (1991) outlined screening
recommendations for children greater than 2 years of age. The panel recommends
selective lipoprotein or total cholesterol screening of children with the following risk
factors:
1. A family history of premature cardiovascular disease, which was defined as having
a parent or grandparent age 55 years or younger who were found to have coronary
atherosclerosis diagnosed by coronary arteriography.
2. Parents or grandparents 55 years of age or less who suffered a documented
myocardial infarction, angina pectoris, peripheral vascular disease, cerebrovascular
disease, or sudden cardiac death.
3. A parent with high blood cholesterol (240 mg/dL or higher).
4. Other risk factors, particularly when familial history is not available. Risk factors
include: obesity (weight for height >_ 95th percentile), hypertension, diabetes
mellitus and physical inactivity.
Table 1 lists the panel's recommendations concerning classification of total and LDL-cholesterol
levels in children at risk.
Table 1
Classification of Total and LDL-Cholesterol Levels
in Children and Adolescents from Families with
Hypercholesterolemia or Premature Cardiovascular Disease
Category Total Cholesterol LDL Cholesterol
Acceptable < 170 mg/dL < 110 mg/dL
Borderline 170-199 mg/dL >_ 130 mg/dL
High 2. 200 mg/dL £. 130 mg/dL
The long-term risks of obesity in children have primarily to do with increased risk of
remaining obese into adulthood, carrying the metabolic disturbances which predispose to
increased risk of premature atherosclerotic heart disease, diabetes, and possibly cancer.
The short-term risks of obesity in children are mostly psychosocial.
Risk of Persistence of Obesity
Infant fatness at birth does not predict fatness at age one year (Whitelaw, 1977), and a
high level of fatness in infancy is not a strong predictor of obesity in childhood, although
2
the risk may be slightly higher than random (Peck and Ullrich, 1985). By early childhood,
tracking of relative fatness is stronger, and increases with age. Obese children are more
likely to become obese adults than are normal-weight or underweight children (Abraham et
al., 1971; Rimm and Rimm, 1976). Stark et al. (1981) examined childhood and adult
weight and height data from 5,362 children born in 1946 and concluded that the risk of
overweight in adulthood was related to the degree of overweight in childhood and was
about 40% for overweight seven-year-olds. Mossberg (1989) conducted a 40-year follow
up study of obese children and found that while obese children had greater than normal
weights as adults, the best predictors for adult obesity were family history of obesity and
severe obesity at puberty. Freedman et al. (1987) examined the persistence of obesity and
overweight over an eight-year period in the Bogalusa Heart Study. Subjects were children
initially aged two to fourteen years. Of the 222 children who had initial triceps skinfold
values above the 85th percentile of reference data, 43 percent were obese eight years
later. Triceps skinfold relative values tracked most strongly in Black females (r = 0.64) and
somewhat less well for White females (r = 0.45). The persistence of obesity was increased
by initial age (greater than five years) and the severity of early obesity. Sorensen and
Sonne-Holm (1988) also reported that severely overweight children are at a much elevated
risk for adult obesity. There is a dearth of information on the persistence of obesity in
children younger than age approximately three years, but what evidence there is suggests
that risk of persistence is lower at younger ages.
Although the obese child has an elevated risk of adult obesity, most obese adults were not
obese as children (Rimm and Rimm, 1976; Hartz and Rimm, 1980). That is, the prevalence
of obesity in the U.S. population increases steadily with age after adolescence, and most
adult obesity is not a consequence of childhood obesity.
Psvchosocial Risks
Perhaps the most damaging effects of obesity in children are social and psychological in
nature; they may have long-term consequences for self-esteem and social adjustment. The
obese child's size may cause adults and other children to expect the child to behave in a
manner appropriate for an older child. In addition, obese children experience various forms
of discrimination. Children as young as five years old rank obese children as less desirable
playmates than disabled or disfigured children (Staffieri, 1987; Richardson et al., 1961).
The fat child is often teased or excluded from play (Wolff, 1962). Lack of participation in
play activities may further promote obesity by limiting exercise; more important, feelings of
inadequacy and poor self-esteem can result (Wadden et al., 1984). While there is debate
about the universality of this phenomenon (Kaplan and Wadden, 1986), the psychosocial
effects of childhood obesity are certainly damaging to at least some children.
ETIOLOGY OF CHILDHOOD OBESITY
The relative roles of genetic and environmental contributions to obesity in children are as
yet undefined. It is well documented that obesity tends to run in families (Garn and Clark,
1976; Garn et al., 1989) and that children are most likely to be obese when both parents
are obese, and least likely to develop obesity when both parents are lean. Price et al.
(1989) showed that children of obese parents are more likely to develop persistent obesity
than other children.
^b
In spite of evidence for e significant genetic component to risk of developing obesity (Price
et al., 1989; Stunkard et al., 1990), the increasing prevalence of obesity in the childhood
population supports the assumption that environment plays a role (Gortmaker et al., 1987).
The two likely candidates for environmental influence, of course, are food intake and
physical activity.
Food Intake
Data from the NHANES I and NHANES II surveys show no secular change in mean energy
intakes among children (Gortmaker et al., 1990), in spite of an increasing prevalence of
obesity during the same period. Several studies have compared food intake of lean and
obese subjects. Some have reported greater intakes in the obese (Waxman and Stunkard,
1980); however, most indicate that obese subjects do not eat significantly more than their
lean peers (Rolland-Chachera and Bellisle, 1986; Frank et al., 1978). Most studies have
been in adults (Keen et al., 1979; McCarty, 1966; Kromhout, 1983; Bingham et al., 1981),
and adolescents (Johnson et al., 1956; Stefanick et al., 1959; Hamptom et al., 1967) and
a few in infants (Vobecky et al., 1983; Mumford and Morgan, 1982). Vobecky et al.
(1983) found that energy intake per kg body weight was lower in infants with relative
weights > 105% of expected weight than in leaner infants. The overwhelmingly consistent
finding across a wide range of ages is fairly large variation in energy intakes within groups
of both obese and lean subjects, including preschool children (Huenemann, 1974).
There are only a few studies which report dietary and nutrient intake patterns among obese
children except for energy intake. Valoski and Epstein (1990) studied 21 eight-to-twelve-year-
old children and found no significant differences between lean and obese children with
respect to intakes of calories, iron, vitamin A. vitamin C, thiamin, or riboflavin. Rolland-
Chachera and Bellisle (1986) found a significant correlation between degree of adiposity of
one-to-three-year-old British children and percent of calories from protein in the diet, but
not with percent of calories from fat. Frank et al. (1978) also reported higher protein
intakes in a group of 185 ten-year-old children in the Bogalusa Heart Study with high body
mass index; when triceps skinfold was the index for obesity, however, saturated fat intake
was the only dietary component associated with increasing adiposity. Both Rolland-
Chachera and Bellisle (1986) and Whitelaw et al. (1971) have speculated that the increased
proportion of obesity among lower social class children in Britain may be related to
relatively higher levels of carbohydrate intake.
Energy Expenditure
Lack of physical activity plays an important role in the development of obesity, although
variation in physical activity alone does not explain within-sample differences in adiposity
among school-aged children (Ross and Gilbert, 1985). Dietz and Gortmaker (1985) report a
direct association between television viewing and obesity in children. The genetic
component of energy expenditure may be significant as well. Griffiths and Payne (1976)
showed that the resting metabolic rate of normal-weight four-year-old children of obese
parents was ten percent lower than that of children of nonobese parents, even though the
two groups of children had similar heights and weights. Roberts et al. (1988) reported that
lower energy expenditure at three months of age was predictive of overweight at age one
year.
HI
Other Associated Factors
There ere significent regional differences in prevalence of childhood obesity, with the
highest rates in the Northeast and the Midwest, and in cities (Dietz and Gortmaker, 1984),
independent of race end socioeconomic status. In developed countries including the U.S.,
women of low socioeconomic status are more likely to be obese than those of higher
socioeconomic status (Sobel and Stunkard, 1989); a similar association has been observed
in children {Stunkard et al., 1972).
MANAGEMENT OF OBESITY IN CHILDREN
Much uncertainty exists with regard to optimal management of obesity in children. The
only major items of consensus are a) that diet regimes should be nutritionally adequate to
support normal growth; b) that physical activity is important; and c) that models for
management of obesity in adults cannot simply be transferred to children. There is some
indication that family-based treatment is most effective, and that effective treatment of
obesity in childhood may have lasting effects.
The Committee on Nutrition of the American Academy of Pediatrics (1981) states "caloric
restriction to the point of weight loss should not be used for children, whose statural
growth and central nervous system development could be impaired by a prolonged
catabolic state. Growth of the child's lean mass should be supported, and the child's
adipose mass should be held constant." The diet should be adequate in vitamins, minerals,
and protein to meet requirements for growth, and growth in stature should be monitored as
an indicator of dietary adequacy. The Committee warns against subjecting infsnts to low-fat
milk feedings which may present excessively high renal solute loads. There is also
some concern that low-fat or overly dilute feedings may cause a young child to learn
behaviors inappropriate for future caloric regulation, such as increased volume ingestion
(Committee on Nutrition, 1981).
Successful programs for the treatment of childhood obesity have emphasized appropriate
diet, physical activity, self-esteem development, and behavior modification (Jonides, 1990);
Epstein and Wing, 1987). Leung and Robow (1990) have pointed out that because of the
strong familial link in the development of obesity in children, treatment programs for long
term weight loss should involve the entire family. Every member of the family should
support the overweight child and adjust eating and behavior habits to conform to the
healthier lifestyle. Physical activity and decreasinq sedentary time by limiting television
viewing are particularly important components of the management of obesity (Gortmaker et
al., 1990).
Valoski and Epstein (1990) reported an 18.3 percent everege reduction in overweight while
linear growth was not affected after six months of a family-based behavioral weight control
program for 8-12 year old children. Diet, exercise and behavioral management were
included in the program. Nutrition education was a key component of the program and
emphasis was placed on nutrient density of foods. The same researchers reported similar
success (Epstein et al., 1986) in 1-6 year old children. The diet wes modified to increase
iron and calcium intakes. Emphssis wes placed on the basic four food groups and on
making low calorie choices in each food group. A decrease in overweight of 15.4 percent
was reported over a ten-week period.
Epstein et al. (1990) have demonstrated that effective treatment of obesity in children can
produce effects into adulthood (Stunkard and Berkowitz, 1990). They conducted a ten-year
follow up study of 75 obese six-to-twelve-year-old children who were treated by diet,
exercise, and behavioral change weekly for eight weeks, followed by six monthly and three
long-term follow up meetings. The dietary component emphasize nutritional foods along
with elimination of high sugar and high fat foods. Children who participated in the program
with their parents showed significantly greater decreases in percent overweight five and
ten years later, compared with controls who attended meetings and received the
information, but without behavioral change strategies including contracting, self-monitoring,
social reinforcement, modeling, and contingency management. Over the long run,
decreased intake of high calorie foods was predictive of success. Long-term successful
weight loss by obese parents did not occur, but parental support of the child's efforts was
critical to long-term success for the child.
Virtually all successful treatment programs for obese children emphasize nutrient dense
foods and sensible eating plans including a variety of foods. More nutrient dense foods can
replace less nutritious, calorically dense foods in the diet; by so doing, the child improves
dietary quality while learning better eating habits.
SUMMARY
The prevalence of obesity among children in the U.S. has increased significantly in the last
two decades. The problem is especially prevalent among Mexican-American and Native
American children, but the increase in prevalence has affected all ethnic groups and
socioeconomic levels. While most obese children do not become obese adults, they do
bear an increased risk of adult obesity and its attendant health hazards, and obesity is a
risk factor for elevated serum cholesterol even in early childhood.
Low levels of physical activity and family history of obesity seem to be the most important
as predictors of obesity in children; overfeeding is much less important as an etiologic
factor. Treatment of obesity in childhood requires a long-term approach including careful
attention to nutritional quality of the diet in order to support normal growth and
development and increased physical activity.
6
qq
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5^
Technical Paper 5
Hematological Standards for Risk