Obesity and the environment: Where do we go from here

The obesity epidemic shows no signs of abating. There is an urgent need to push back against the environmental forces that are producing gradual weight gain in the population. Using data from national surveys, we estimate that affecting energy balance by 100 kilocalories per day (by a combination of reductions in energy intake and increases in physical activity) could prevent weight gain in most of the popu-lation. This can be achieved by small changes in behavior, such as 15 minutes per day of walking or eating a few less bites at each meal. Having a specific behavioral target for the prevention of weight gain may be key to arresting the obesity epidemic. There is no sign that the rapid increase in obesity seen over the past two decades is abating. Recent data from the 1999–2000 National Health and Nutrition Examination Survey (NHANES) (1) show that almost 65% of the adult population in the United States is overweight, which is defined as having a body mass index (BMI) greater than 25 kg/ m2, compared to 56 % seen in NHANES III, conducted between 1988 and 1994 (1). The prevalence of obesity, defined as BMI greater than 30 kg/m2, has increased dramatically from 23 to 31 % over the same time period. Children are not immune to the epidemic, with the prevalence of obesity in children and adolescents up by 36 % (from 11 to 15%) during this time. The future is not hopeful unless we act now. BMI distributions esti-mated from the last two NHANES studies are shown in Fig. 1. When we projected the data to 2008, assuming that weight gain continues at the present rate, we found that the obesity rate in 2008 will be 39%. The rest of the world is catching up. The World Health Or-ganization (WHO) has declared overweight as one of the top ten risk conditions in the world and one of the top five in developed nations (2). Worldwide, more than one billion adults are overweight and over 300 million are obese (2). Most countries are experienc-ing dramatic increases in obesity. As an ex-ample, the prevalence of overweight individ-uals in China doubled in women and almost tripled in men from 1989 to 1997 (3). Obesity increases the risk for type 2 diabe-tes, cardiovascular disease, and some cancers (4). Particularly disturbing is the 10-fold in-crease in incidences of type 2 diabetes amon