Excessive weight is a major health problem in the United States and other affluent societies. For a number of years, obesity was said to be epidemic—strictly defined, this implies a temporary widespread outbreak of greatly increased frequency and severity. Unfortunately, obesity more correctly is endemic—a condition that is habitually present. By 1991, approximately a third of adults in the United States were overweight, and thus a stated goal of Healthy People 2000 was to reduce the prevalence of overweight people to 20 percent or less by the end of the 20th century (Public Health Service, 1990). Not only was this goal not achieved, but by 2000, more than half of the population was overweight. In 2010, a third of all adults were obese (Ogden, 2012).
The adverse health aspects of obesity are staggering. Obesity-related diseases include diabetes, heart disease, hypertension, stroke, and osteoarthritis. Obese women who become pregnant—and their fetuses—are predisposed to various serious pregnancy-related complications. Moreover, long-term maternal and fetal effects include significant and increased morbidity and mortality rates.
A number of systems have been used to define and classify obesity. The body mass index (BMI), also known as the Quetelet index, is currently most often used. The BMI is calculated as weight in kilograms divided by the square of the height in meters (kg/m2). Calculated BMI values are available in various chart and graphic forms, such as the one shown in Figure 48-1. The National Institutes of Health (2000) classifies adults according to BMI as follows: normal (18.5 to 24.9 kg/m2); overweight (25 to 29.9 kg/m2); and obese (≥ 30 kg/m2). Obesity is further divided into: class 1 (30 to 34.9 kg/m2); class 2 (35 to 39.9 kg/m2); and class 3 (≥ 40 kg/m2).
Chart for estimating body mass index (BMI). To find the BMI category for a particular subject, locate the point at which the height and weight intersect.
By 2000, 28 percent of men and 33 percent of women were obese (Ogden, 2012). For the period 2009 to 2010, among men and women these percentages were almost identical at approximately 35 percent. Shown in Figure 48-2 are the prevalences of obesity among girls and women. Obesity increases with age as well as with ethnic minority, and almost 60 percent of black women were obese in 2010. This is also true among indigent individuals (Drewnowski, 2004).
Prevalence of obesity in girls and women in the United States for 2009–2010. (Data from Flegal, 2012; Ogden, 2012.)