Editors' ChoiceObesity

Survey Says: Obesity Prevalence Plateaus

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Science Translational Medicine  17 Feb 2010:
Vol. 2, Issue 19, pp. ec26
DOI: 10.1126/scitranslmed.3000959

Just last week, U.S. first lady Michelle Obama officially announced the "Let's Move" campaign to curb childhood obesity, and no wonder. Nearly one-third of America's children are overweight or obese, and they are joined by close to two-thirds of adults. The prevalence of obesity and overweight in the U.S. adult population rose dramatically between 1976 and 1994. Indeed, the prevalence of individuals with a body mass index (BMI) greater than 30 kg/m2 increased by 8% during this time span, on the way to the current levels of 32% in men and 35.5% in women. Similarly in children, the prevalence of high BMI for age—defined as a BMI greater than the age-adjusted 95% percentile—tripled since 1980, swelling to ~17% across different ages and ethnic groups. However, some welcome data recently reported in JAMA suggest a leveling off in the prevalence of obesity in adults and high BMIs in children.

Indeed, the most recent 2007-2008 National Health and Nutrition Examination Survey (NHANES) data analyzed by Flegal et al. and Odgen et al. indicate that a plateauing in the prevalence of obesity began to take shape over the past 7 and 10 years in adults and children, respectively. NHANES is a series of cross-sectional random samples of U.S. children and adults collected every few years, starting in 1960 and reaching sample sizes of ~6,000 adults and more than 4,000 children in each survey. Between the 1999–2000 and 2007–2008 NHANESs, the prevalence of obesity increased significantly in men from 27.5% [95% Confidence Interval (CI): 24.4% to 30.6%] to 32.3% [95% CI: 29.5% to 35.0%]. In contrast, the prevalence of obesity in men remained stable between the 2003–2004 and 2007–2008 surveys [31.1% (95% CI: 28.5 to 33.7) and 33.3% (95% CI: 29.3% to 37.4%), respectively]. This general pattern was consistent in women, except that the plateau occurred over a longer period of time; the prevalence of obesity ranged from 33.2% [95% CI: 29.7% to 36.6%] to 35.5% [95% CI: 33.2% to 37.7%] between the 1999-2000 and 2007-2008 surveys. In children, the high BMI prevalence was stable between the 1999–2000 and 2007–2008 surveys, but remains high at ~16.9% [95% CI: 14.1% to 19.6%].

The interpretation of these obesity patterns is particularly challenging, because the studies rely on BMI as the measure of obesity. The BMI is calculated as (weight in kilograms) divided by (height in meters)2 and does not measure adiposity directly. Thus, it is possible that body composition has continued to change in an unfavorable manner over the time encompassed by the various surveys. Many individual and population-level health interventions targeted at lowering obesity levels have been developed and tested over the last decade with mixed results. It remains unclear whether the new trends indicate that these interventions have had a measure of success, given that the physiological mechanisms that spurred the obesity increase in the first place are unknown. One conclusion that can be reached from the survey results is that, despite a leveling, the prevalence of obesity remains high. To truly tackle this human health problem, scientists must seek further insights into the biological and behavioral triggers of obesity.

K. M. Flegal et al., Prevalence and trends in obesity among U.S. adults, 1999-2008. JAMA 303, 235–241 (2010). [Abstract]

C. L. Ogden et al., Prevalence of high body mass index in U.S. children and adolescents, 2007-2008. JAMA 303, 242–249 (2010). [Abstract]

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