he Epidemiology of Obesity

n the United States, obesity among adults and verweight among children and adolescents have ncreased markedly since 1980. Among adults, obeity is defined as a body mass index of 30 or greater. mong children and adolescents, overweight is dened as a body mass index for age at or above the 5th percentile of a specified reference population. n 2003–2004, 32.9% of adults 20 –74 years old were bese and more than 17% of teenagers (age, 12–19 ) were overweight. Obesity varies by age and sex, nd by race-ethnic group among adult women. A igher body weight is associated with an increased ncidence of a number of conditions, including dibetes mellitus, cardiovascular disease, and nonaloholic fatty liver disease, and with an increased isk of disability. Obesity is associated with a modstly increased risk of all-cause mortality. However, he net effect of overweight and obesity on morbidty and mortality is difficult to quantify. It is likely hat a gene-environment interaction, in which geetically susceptible individuals respond to an enironment with increased availability of palatable nergy-dense foods and reduced opportunities for nergy expenditure, contributes to the current high revalence of obesity. Evidence suggests that even ithout reaching an ideal weight, a moderate mount of weight loss can be beneficial in terms of educing levels of some risk factors, such as blood ressure. Many studies of dietary and behavioral reatments, however, have shown that maintenance f weight loss is difficult. The social and economic osts of obesity and of attempts to prevent or to reat obesity are high.