he prevalence of obesity in the United States and the world has risen to epidemic/pandemic proportions. This increase has occurred despite efforts by healthcare providers and consumers alike to improve the health-related behaviors of the population and a tremendous push from the scientific community to better understand the pathophysiology of obesity. This epidemic is all the more concerning given the clear association between excess adiposity and adverse health consequences such as cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM). These risks associated with overweight/obesity are primarily related to the deposition of excess adiposity or body fatness. Weight loss, specifically loss of body fat, is associated with benefits in all of the obesity-related comorbidities, but, unfortunately, most weight loss interventions are associated with weight regain and are therefore not successful in the long term. It is for these reasons that efforts to prevent weight gain and overweight/ obesity are necessary. This is especially important when one considers younger individuals, who have even more to lose as a consequence of a longer duration of excess adiposity.After a brief review of the epidemiology of obesity, this statement will make the case for the importance of weight gain prevention. This argument will first include a review of the complications of overweight and obesity in both adults and children, including the future CVD risks of obesity in early life. Energy balance dysregulation and adaptations to the weight-reduced state, favoring weight regain, will then be reviewed as further argument for the need for obesity prevention. This will be followed by a discussion on the goals and strategies for accomplishing the difficult task of the prevention of weight gain and obesity.
Scope of the Problem Classification of Overweight and ObesityThe body mass index (BMI) is the most widely used and accepted method for the assessment and classification of excess adiposity or body fatness. Overweight and obesity are classified according to BMI for adults. 1 A BMI Ͻ18.5 kg/m 2 is considered underweight, between 18.5 and 24.9 kg/m 2 corresponds to a healthy weight, between 25.0 and 29.9 kg/m 2 is overweight, and Ն30.0 kg/m 2 is obese. Obesity is further classified as stage I or mild (BMI of 30.0 to 34.9 kg/m 2 ), stage II or moderate (BMI of 35.0 to 39.9 kg/m 2 ), and stage III or severe (BMI of Ն40.0 kg/m 2 ). In children, BMI percentiles adjusted for age and sex and calculated on the basis of a compilation of national survey data collected over a 30-year period are used. In children aged 2 to 19 years, overweight is defined as a BMI between the 85th and 95th percentiles, and obesity is defined as a BMI Ն95th percentile. 2
Epidemiology of Overweight and ObesityThe prevalence of overweight and obesity in the United States and the world has risen dramatically over the last 4 to 5 decades and has been summarized. 3,4 In the most recent US population estimates based on data from the 2007-2008 National Health and Nutri...
