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Overweight
and Obesity
Obesity Trends
Prevalence of Overweight and Obesity Among Adults: United States, 1999-2000
Results from the 1999-2000
National Health and Nutrition Examination Survey (NHANES), using measured
heights and weights, indicate that an estimated 64 percent of U.S. adults
are either overweight or obese. As shown in table
1, this represents a prevalence that is approximately 8 percent
higher than the age-adjusted overweight estimates obtained from NHANES
III (1988-94).
Body mass index (BMI),
expressed as weight/height2 (BMI; kg/m2), is commonly
used to classify overweight (BMI 25.0-29.9) and obesity (BMI greater than
or equal to 30.0) among adults (age 20 years and over). When age-adjusted
prevalence estimates from the NHANES III for adults age 20-74 years were
compared with prevalence estimates from NHANES II (1976-80), there were
notable increases in the prevalence of persons who were either overweight
or obese (BMI greater than or equal to 25.0), as shown in table
2. Most of this increase was attributable to increases in
the obese category (BMI greater than or equal to 30.0), whereas only minor
increases occurred in the prevalence of persons who are overweight but
not obese (BMI 25.0-29.9).
To assess changes in overweight
and obesity that have occurred since the 1988-94 time period, prevalence
estimates for adults age 20 years and over who participated in the 1999-2000
NHANES were compared with those of the NHANES III. NHANES III and NHANES
1999-2000 used a stratified, multistage, probability sample of the civilian,
U.S. noninstitutionalized population. A household interview and a physical
examination were conducted for each survey participant. During the physical
examination, conducted in mobile examination centers, height and weight
were measured as part of a more comprehensive set of body measurements.
These measures were taken by trained health technicians, using standardized
measuring procedures and equipment. Observations for pregnant women and
for persons missing a valid height or weight measurement were not included
in the data analysis.
One of the national health
objectives for 2010 is to reduce the prevalence of obesity among adults
to less than 15 percent. However, the NHANES 1999-2000 data for persons
age 20 years and over suggest an increase in the proportion of obese adults
in the United States, where the estimated age-adjusted prevalence moved
upward from a previous level of 23 percent to a new level of approximately
30 percent. Among adults age 20-74 years, the estimated prevalence of
obesity (BMI greater than or equal to 30.0) has doubled between NHANES
II and NHANES 1999-2000, from approximately 15 percent to an estimated
31 percent.
Table 1. Age-adjusted* prevalence of overweight
and obesity among U.S. adults among U.S. adults, age 20 years and over
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NHANES III (1988-94)
(n=16,679)
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NHANES 1999-2000
(n=4,115)
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Overweight or
obese (BMI greater than or equal to 25.0)
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56
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64
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Obese (BMI greater
than or equal to 30.0)
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23
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30
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*Age-adjusted by the direct method to the year 2000 U.S. Bureau of
the Census estimates using the age groups 20-39, 40-59, and 60 years and
over.
Table 2. Age-adjusted* prevalence of overweight
and obesity among U.S. adults, age 20-74 years
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NHANES II (1976-80)
(n=11,207)
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NHANES III (1988-94)
(n=14,468)
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NHANES 1999-2000
(n=3,601)
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Overweight or
obese (BMI greater than or equal to 25.0)
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47
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56
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64
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Obese (BMI greater
than or equal to 30.0)
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15
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23
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31
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*Age-adjusted by the direct method to the year 2000 U.S. Bureau of
the Census estimates using the age groups 20-39, 40-59, and 60-74 years.

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