Rationale

An estimated 97 million adults in the United States are overweight or obese (1), a condition that substantially raises their risk of morbidity from hypertension (2-6), type 2 diabetes (7-10), stroke (11-13), gallbladder disease (14, 15), osteoarthritis (16-18), sleep apnea and respiratory problems (19-21) and endometrial, breast, prostate, and colon cancers (22-24).

As a major contributor to preventive death in the United States today (25), overweight and obesity pose a major public health challenge. Not only is the prevalence of this serious medical condition soaring among adults (between 1960 and 1994, overweight increased from 30.5 to 32 percent among adults ages 20 to 74 and obesity increased from 12.8 percent to 22.5 percent), but it is also affecting ever greater numbers of American youth and exacting a particularly harsh toll from low-income women and minorities. The Third National Health and Nutrition Examination Survey (NHANES III) estimated that 13.7 percent of children and 11.5 percent of adolescents are overweight, while a number of smaller, ethnic-specific studies suggest that overweight and obesity may afflict up to 30 to 40 percent of children and youth from minority populations (26, 27).

The prevalence of overweight and obesity in adults in the United States increased markedly during the last decade. According to NHANES III data, 54.9 percent of U.S. adults aged 20 years and older are either overweight or obese; 32.6 percent are overweight, defined as having a body mass index (BMI)* of 25.0 to 29.9 kg/m²; and 22.3 percent are obese with a BMI of 30 kg/m² (1). The panel acknowledges that overweight and obesity are not mutually exclusive; obese persons are also overweight. Since overweight and obesity lead to increased morbidity and mortality, these figures demonstrate the enormity of the public health problem, as well as the clinical problem, of overweight and obesity in this country.

In this report, overweight is defined as a BMI of 25.0 to 29.9 kg/m² and obesity as a BMI of 30 kg/m². The rationale behind these definitions is based on epidemiological data that show increases in mortality with BMIs above 25 kg/m² (28-32). The increase in mortality, however, tends to be modest until a BMI of 30 kg/m² is reached (28, 31, 32). For persons with a BMI of 30 kg/m², mortality rates from all causes, and especially from cardiovascular disease, are generally increased by 50 to 100 percent above that of persons with BMIs in the range of 20 to 25 kg/m² (28, 31, 32).

Overweight and obesity result from a complex interaction between genes and the environment characterized by long-term energy imbalance due to a sedentary lifestyle, excessive caloric consumption,or both (33). They develop in a sociocultural environment characterized by mechanization, sedentary lifestyle, and ready access to abundant food. Attempts to prevent overweight and obesity are difficult to both study and achieve. Indeed, few research efforts have investigated either individual or community-based prevention strategies (34).

A substantial body of research, however, does exist on the health risks of overweight and obesity, and on methods for treatment. This report, which bases its recommendations primarily on published evidence, emphasizes the important role of primary care practitioners in evaluating all overweight and obese adults and promoting weight control through the use of multiple interventions and strategies tailored to particular patient needs. Although the recommendations and guidelines included in this report focus on the clinical assessment and treatment of overweight and obese patients, a second important goal is to encourage primary care practitioners to take an active role in preventing inappropriate weight gain among all of their patients.

*The BMI is calculated as follows: BMI=weight (kg)/height squared (m²). Conversion [weight (pounds)/height (inches)²] x 703 (1 lb=0.45 kg) (1 in.=2.54 cm=0.0254 m). A BMI of 25 is equivalent to 184 lb in a 6'0" person and to 155 lb in one 5'6". A BMI of 30 is equivalent to 221 lb in a 6'0" person and to 186 lb in one 5'6". (The conversion of BMI according to weight for height is provided in Appendix V.)