Excess weight and a sedentary lifestyle have long been regarded as self-inflicted conditions with largely personal consequences. A rapidly growing body of data from basic research, national health surveys, epidemiologic studies, and limited randomized trials, however, is revealing the enormous public health impact of this intricately linked to at least 300 000 premature deaths, substantial morbidity, and more than $90 billion dollars in direct health care costs each year in the United States alone. Despite this impact, excess weight and physical inactivity have not received the same attention from clinicians and policy makers as has been focused on tobacco use, which has a similar impact on public health.
Powerful social and cultural trends drive the pandemic of excess weight and inactivity, and numerous obstacles make it difficult to maintain a healthy weight and engage in sufficient daily exercise. Health care providers can help check this perilous trend by making their patients aware of the problem and helping them overcome these barriers. Clinicians have direct and personal access to many high-risk individuals, the opportunity to educate patients about their personal risks, the stature to suggest lifestyle changes, and the authority to encourage specific sustained changes in behavior that can lead to a healthier weight and more active lifestyle. To do this, clinicians must be able to identify high-risk patients, feel comfortable and empowered to broach the subject of weight control and physical activity, offer behavioral strategies that lead to effective and long-lasting improvements in these variables, and understand the indications for considering pharmacologic and/or surgical management. Given the high prevalence of overweight and inactivity in the United States, helping even a small percentage of patients achieve or maintain a healthier weight and engage in higher levels of physical activity would have a substantial impact on public health.
Trends in Overweight/Obesity and Inactivity
National surveys, which have tracked weight and physical activity in the United States for more than 40 years, show a population that is increasingly overweight and inactive. In the First National Health and Nutrition Examination Survey (NHANES I, 1960-1962), an estimated 31.6% of adult men and women met the current definition for overweight (body mass index [BMI; calculated as weight in kilograms divided by the square of height in meters] of 25.0-29.9) and 13.4% were obese (BMI 30). By the NHANES survey of 1999-2000, the proportion of overweight adults had increased only slightly, while the proportion of obese adults had risen dramatically. Between 1991 and 2001, the annual Behavioral Risk Factor Surveillance System recorded a 74% increase in the prevalence of obesity. Applying data from the latest NHANES survey, an estimated 131 million American adults are overweight or obese.
The prevalence of overweight and obesity in children and adolescents is rising in parallel with that in adults. An estimated 15% of those aged 6 to 19 years are considered overweight or obese. Early obesity not only increases the likelihood of adult obesity, but it also increases the prevalence of weight-related risk factors for cardiovascular disease such as hypertension, elevated serum cholesterol levels, and insulin resistance. Indeed, excess weight has been associated with the surprising and dramatic recent increase in diagnoses of type 2 diabetes mellitus (formerly called adult-onset diabetes) among children. In some parts of the United States, more than 30% of new cases of type 2 diabetes mellitus are in children, and most of these are attributable to obesity. Physical activity among children is also decreasing. Daily participation in high school physical education classes, for example, declined throughout the 1990s, from 34.2% of students physically active for 20 minutes or more per day in physical education classes in 1991 to 21.7% in 1997. A recent survey of third grade children in 684 schools showed an average of 25 minutes per week of moderate to vigorous activity in physical activity classes. Walking and bicycling by children aged 5 to 15 years declined 40% between 1977 and 1995, while the time spent in sedentary activities such as watching television, playing video games, or using a computer has dramatically increased.
Data from numerous cohort and metabolic studies provide consistent evidence linking excess weight and inactivity with impaired health. Excess weight increases the risks of metabolic disorders such as hypertension, dyslipidemia, insulin resistance, and glucose intolerance. In the Marks and Spencer Cardiovascular Risk Factor Study of 14 077 middle-aged women, highly significant age-adjusted differences were observed across 7 categories of BMI (<20 to 30) for systolic and diastolic blood pressure and levels of serum total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides, apolipoprotein A-I, apolipoprotein B, and fasting blood glucose. Excess weight is associated with increases in inflammatory markers such as C-reactive protein and fibrinogen in adults and children, increases that have been associated with elevated risks of cardiovascular disease. Excess weight is also strongly linked to increased risks of coronary heart disease, ischemic stroke, type 2 diabetes mellitus, osteoarthritis, gallbladder disease, some types of cancer, and other conditions. Physical inactivity is associated with a similarly extensive range of health problems, including hypertension, dyslipidemia, insulin resistance, type 2 diabetes, obesity, coronary heart disease, ischemic