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Ogden CL, Flegal KM, Carroll MD, Johnson CL. Prevalence and Trends in Overweight Among US Children and Adolescents, 1999-2000. JAMA. 2002;288(14):1728–1732. doi:10.1001/jama.288.14.1728
Context The prevalence of overweight among children in the United States increased
between 1976-1980 and 1988-1994, but estimates for the current decade are
Objective To determine the prevalence of overweight in US children using the most
recent national data with measured weights and heights and to examine trends
in overweight prevalence.
Design, Setting, and Participants Survey of 4722 children from birth through 19 years of age with weight
and height measurements obtained in 1999-2000 as part of the National Health
and Nutrition Examination Survey (NHANES), a cross-sectional, stratified,
multistage probability sample of the US population.
Main Outcome Measure Prevalence of overweight among US children by sex, age group, and race/ethnicity.
Overweight among those aged 2 through 19 years was defined as at or above
the 95th percentile of the sex-specific body mass index (BMI) for age growth
Results The prevalence of overweight was 15.5% among 12- through 19-year-olds,
15.3% among 6- through 11-year-olds, and 10.4% among 2- through 5-year-olds,
compared with 10.5%, 11.3%, and 7.2%, respectively, in 1988-1994 (NHANES III).
The prevalence of overweight among non-Hispanic black and Mexican-American
adolescents increased more than 10 percentage points between 1988-1994 and
Conclusion The prevalence of overweight among children in the United States is
continuing to increase, especially among Mexican-American and non-Hispanic
The prevalence of overweight among children in the United States has
been increasing. Between the 1960s and 1988-1994, the prevalence among 6-
through 11-year-old children increased from 4% to 11%. During this same period,
the prevalence among 12- through 19-year-olds increased from 5% to 11%.1 Overweight children often become overweight adults,2 and overweight in adulthood is a health risk.3 Although childhood overweight may not result in adult
health risk,4 immediate consequences of overweight
in childhood are often psychosocial and also include cardiovascular risk factors
such as hypertension, high cholesterol levels, and abnormal glucose tolerance.5
This article presents the most recent national estimates of overweight
prevalence in US children. It is based on examination data from the 1999-2000
National Health and Nutrition Examination Survey (NHANES).
NHANES is a series of cross-sectional, nationally representative examination
surveys conducted by the National Center for Health Statistics of the Centers
for Disease Control and Prevention. Beginning in 1999, NHANES became a continuous
survey. The procedures followed to select the sample and conduct the interviews
and examinations were similar to those for previous surveys. Two or more years
of data are necessary to have adequate sample sizes for subgroup analyses.
This report is based on the first 2 years of the continuous NHANES data collection
(1999-2000). Previous survey results presented include NHANES III conducted
from 1988-1994,6 NHANES II conducted from 1976-1980,7 NHANES I conducted from 1971-19748;
the National Health Examination Survey (NHES) cycle 3 conducted from 1966-19709; and NHES cycle 2 conducted from 1963-1965.10
NHANES 1999-2000 is a nationally representative cross-sectional survey
of the total civilian noninstitutionalized population in the United States.
The design was a stratified multistage probability sample based on selection
of counties, blocks, households, and persons within households. NHANES 1999-2000
was designed to oversample Mexican Americans, non-Hispanic blacks, and adolescents
to improve estimates for these groups.
All surveys included a standardized physical examination with measurement
of recumbent length, stature, and weight. Recumbent length was measured in
children younger than 4 years and stature in children aged 2 years or older.
The NHANES 1999-2000 sample included weight and height measurements for 4722
children and youth from birth through age 19 years.
Overweight prevalence from NHANES 1999-2000 was estimated by age at
examination, sex, and race/ethnicity. Race/ethnicity was reported by a member
of the household. For the purposes of this analysis, children were categorized
as non-Hispanic white, non-Hispanic black, Mexican American, or other. Numbers
for racial/ethnic groups in the "other" category were too small for meaningful
analysis when considered separately, but these children were included in the
totals. Trend estimates based on all the surveys were estimated by age at
examination and sex. Trend estimates by race/ethnicity are available only
for NHANES III and NHANES 1999-2000 because these were the only surveys with
comparable racial/ethnic information.
The definition of overweight among children is a statistical definition
based on the 2000 Centers for Disease Control and Prevention growth charts
for the United States.11 Overweight is defined
as at or above the 95th percentile of body mass index (BMI; calculated as
weight in kilograms divided by the square of height in meters) for age. At
risk for overweight is defined as at or above the 85th percentile, but less
than the 95th percentile of BMI for age. The BMI-for-age growth charts were
developed from 5 of the national data sets used in this analysis (NHES 2 and
NHES 3; NHANES I and NHANES II; and NHANES III for children <6 years).
The Committee on Clinical Guidelines for Overweight in Adolescent Preventive
Services recommended use of the 95th percentile of BMI to classify adolescents
as overweight.12 There are no BMI-for-age references
or consistent definitions for overweight for children younger than 2 years.
However, nutrition programs such as the Special Supplemental Nutrition Program
for Women, Infants and Children have used weight-for-length recommendations
to determine overweight and thus program eligibility.13,14 Consequently,
overweight in this age group is defined as at or above the 95th percentile
of weight for length.
For adults 20 years or older, the definition of obesity recommended
by the National Heart, Lung, and Blood Institute and the World Health Organization
is a BMI of 30 or higher.15,16 We
calculated the percentage of 12- through 19-year-old adolescents that met
the adult definition of obesity.
Data were analyzed using SAS (Version 8.02; SAS Institute Inc, Cary,
NC) and SUDAAN (Version 8.0; Research Triangle Institute, Research Triangle
Park, NC) statistical software programs. All analyses included sample weights
that account for the unequal probabilities of selection, oversampling, and
nonresponse. The SEs were estimated using the SUDAAN program. The SEs for
NHANES 1999-2000 were estimated by means of the delete 1 jackknife method.17 For NHES and prior NHANES, the Taylor series linearization
method was used to estimate SEs. Both methods incorporate the sample weights
and account for the complex sample design.
Differences by sex, age group, race/ethnicity, and survey were tested
univariately at the .05 significance level using the t statistic.
Differences between the 3 most recent surveys only were tested for statistical
significance. These 3 surveys were independently designed and independently
drawn with no intended overlap. Therefore, in testing differences between
surveys, a covariance of zero was assumed. For racial/ethnic differences within
age and age differences within race/ethnicity, the Bonferroni method of multiple
comparisons was applied. Because there were 3 implied comparisons, the α
level was .05 divided by 3 (a value of .01667).
The sample sizes from NHANES 1999-2000 for children by sex, age group,
and race/ethnicity are shown in Table 1.
The prevalence of overweight (BMI for age ≥95th percentile) was approximately
10% for 2- through 5-year-olds and approximately 15% for 6- through 11-year-olds
and 12- through 19-year-olds (Table 2).
The prevalence of overweight among males was not significantly different than
among females, although among Mexican-American adolescents a trend toward
an increase in males was seen (P = .06). Non-Hispanic
black and Mexican-American 2- through 5-year-olds had lower prevalences of
overweight than did the older age groups (P<.001
and P = .002, respectively). Comparisons between
racial/ethnic groups showed that the prevalence of overweight among 12- through
19-year-old non-Hispanic blacks (23.6%) and Mexican Americans (23.4%) was
significantly higher than among non-Hispanic whites (12.7%) (P<.001 for both comparisons).
Among infants from birth through 23 months, 11.4% were overweight (weight
for length ≥95th percentile; Table 3). There were no differences in prevalence between younger boys
and girls. However, as with the older children, there were differences between
racial/ethnic groups. About 10% of non-Hispanic whites were at or above the
95th percentile, whereas 18.5% of non-Hispanic blacks were at or above the
95th percentile (P = .009). Differences by race/ethnicity
within sex were not significant possibly because of the small sample sizes.
Table 4 contains the prevalence
of overweight for preschool and school-aged children and adolescents from
national surveys. The changes between the earlier surveys and NHANES III have
been previously published.1,18,19 After
no change in the prevalence of overweight between NHANES I and NHANES II,
there was an increase between NHANES II and NHANES III. Between NHANES III
and NHANES 1999-2000, the increase in overweight prevalence was the same or
greater than between NHANES II and NHANES III. Overweight has increased 5
percentage points among 12- through 19-year-olds from 10.5% to 15.5% between
NHANES III and NHANES 1999-2000. There was a significant increase in overweight
among non-Hispanic black and Mexican-American adolescents. The prevalence
(95% confidence interval) of overweight for non-Hispanic black adolescents
increased from 13.4% (10.8%-16.0%) to 23.6% (19.4%-27.8%) between 1988-1994
and 1999-2000. For Mexican Americans, the prevalence (95% confidence interval)
increased from 13.8% (9.5%-18.1%) to 23.4% (19.3%-27.5%). Figure 1 shows the increase in overweight from NHANES III to NHANES
1999-2000 for adolescents in each racial/ethnic group. Among non-Hispanic
black males (P<.001) and females (P = .002), the prevalence increased 10 percentage points. Among Mexican-American
males, the prevalence increased 13 percentage points (P<.001). Among all adolescent boys virtually no difference existed
between racial/ethnic groups in 1988-1994 (11.6% of non-Hispanic whites, 10.7%
of non-Hispanic blacks, and 14.1% of Mexican Americans were overweight), whereas
in 1999-2000, 12.8% of non-Hispanic whites, 20.7% of non-Hispanic blacks,
and 27.5% of Mexican-American adolescent boys were overweight.
Analyses based on the adult definition of obesity indicated that 11.2%
of 12- through 19-year-olds had a BMI of 30 or higher. Approximately 10% of
non-Hispanic white females, 20% of non-Hispanic black females, and 16% of
Mexican-American females exceeded the adult definition for obesity. The difference
between non-Hispanic white girls and non-Hispanic black girls was significant
(P = .003). In 1988-1994, the corresponding prevalences
were 7.4%, 13.2%, and 9.2%. The 95th percentile of the BMI for age charts
is greater than 30 for males aged 19.5 years or older and females aged 17.5
years or older.
The prevalence of overweight among US children is continuing to increase.
In 1999-2000, more than 15% of 6- through 19-year-olds were overweight and
more than 10% of 2- through 5-year-olds were overweight. The increase in the
prevalence of overweight between 1988-1994 and 1999-2000 is similar to that
seen between 1976-1980 and 1988-1994. The current increase is particularly
evident among non-Hispanic black and Mexican-American adolescents. The prevalence
in these groups increased more than 10 percentage points between 1988-1994
and 1999-2000. More than 23% of non-Hispanic black and Mexican-American adolescents
were overweight in 1999-2000. These results are consistent with data reported
from the National Longitudinal Survey of Youth in which 21.5% of black and
21.8% of Hispanic 4- to 12-year-olds were overweight in 1998.20 This
study also showed a significant increase in overweight among black, Hispanic,
and white children between 1986 and 1998. More recently, self-reported data
from the Youth Risk Behavior Surveillance System suggested that 10.5% of high
school students were overweight in 2001.21 This
is considerably less than the 15.5% overweight based on measured weight and
height in NHANES 1999-2000.
Overweight is due to an imbalance between dietary intake and energy
expenditure, but the exact reason for the imbalance among children is not
clear. Although diet and physical activity are difficult to measure, especially
in children, poor eating habits are often established during childhood. In
2001, almost 80% of school children did not consume the recommended 5 or more
servings of fruits and vegetables per day.21 Boys
were significantly more likely than girls to have eaten 5 or more servings
per day of fruits and vegetables. This was particularly true for black students.
In terms of physical activity, only about half of individuals aged 12 to 21
years reported regular participation in vigorous physical activity and one
fourth reported no vigorous physical activity in 1996.22 More
females than males and more black females than white females reported being
inactive. Moreover, the percentage of high school students who were enrolled
in physical education classes and who reported being physically active for
at least 20 minutes in physical education classes declined from approximately
81% to 70% during the first half of the 1990s.22
Several disorders have been linked to overweight in childhood. Of particular
concern has been a potential increase in type 2 diabetes mellitus related
to the increase in overweight among children.23 Until
recently, type 2 diabetes mellitus had rarely been seen in children. Although
the prevalence of type 2 diabetes mellitus in adolescents is low (<1%),24 cases are now occurring among many population groups
in the United States, especially among ethnic minorities.25 In
general, children and adolescents diagnosed as having type 2 diabetes mellitus
were overweight, had a family history of type 2 diabetes mellitus, and had
signs of insulin resistance. Impaired glucose tolerance has been shown to
be highly prevalent among children with severe obesity.26 The
increase in type 2 diabetes mellitus has occurred particularly among minority
youth in the United States.27 The increase
in prevalence of overweight seen in our current analysis also occurred primarily
among minority adolescents.
It is not clear what interventions will work most effectively to reduce
the high prevalence of overweight among youth. Changes that have contributed
to the increase in overweight may relate to increasing food portion sizes,
consumption of high-fat, energy-dense fast foods, and an increasingly sedentary
lifestyle. These changes will need to be addressed to prevent overweight in
childhood.28 Interventions may focus on parental
behaviors because parents determine the diet and physical activity practices
of their children.29 School-based programs
also may help to change diet or reduce sedentary behaviors.30
To address the problem of increasing prevalence of overweight in US
children, research will need to focus on reasons for the increase and what
interventions will help reduce the prevalence. Overweight is related to dietary
intake and physical activity, both of which are influenced by social, economic,
and physical environments. Whatever the causes of the increase in overweight
among children, overweight among children in the United States is continuing
to increase and the increase in prevalence is highest among Mexican-American
and non-Hispanic black adolescents.
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