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DEFINITION AND EPIDEMIOLOGY
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Obesity and overweight categories have been defined by examining longitudinal study data that associate a given weight with future adverse health effects. The currently accepted surrogate measure of body fatness is body mass index (BMI) which is measured as weight in kilograms divided by height in meters squared. For adults, a BMI less than 18.5 kg/m2 is underweight, 18.5 to 24.9 kg/m2 is healthy weight, 25.0 to 29.9 kg/m2 is overweight, and greater than or equal to 30 kg/m2 is obese. For children and adolescents, a BMI between the 85th and 95th percentile for age and sex is considered at risk of overweight, and BMI at or above the 95th percentile is considered overweight or obese.
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However, BMI does not account for ethnic differences in skeletal structure or musculature. Body frame size varies dramatically by race/ethnicity from small-framed East Asian adults to larger framed Pacific Islanders. Moreover, conventional cut-points for adult overweight (BMI ≥25 kg/m2) and obesity (BMI ≥30 kg/m2) do not correspond to similar absolute or relative metabolic risk in all ethnic group. As a result, the World Health Organization (WHO) and International Obesity Task Force proposed a lower BMI cut-point to define obesity in South and East Asian adults: 23 kg/m2 for overweight and 25 kg/m2 for obesity.
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Prevalence and Projections
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National surveys performed by the Centers for Disease Control and Prevention in the United States have found a significant increase in the prevalence of overweight and obesity over the past 30 years. In 2003 to 2004, according to data from the National Health and Nutrition Examination Survey (NHANES), 32.2% of adults were obese. Trends among adults have been tracked by repeat NHANES surveys, showing that the ...