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14. Obesity
- Rutgers University Press
- Chapter
- Additional Information
The incidence of obesity has escalated dramatically in the United States in the past twenty years to reach epidemic proportions. This obesity epidemic defines a generation with increased risks of incurring a wide range of unhealthy effects, including high blood pressure, type 2 diabetes, coronary heart disease, stroke, gall bladder disease, and several cancers, especially of the breast, prostate gland, and colon. Obesity has become one of the leading causes of preventable early death in the United States. This chapter will look at what the possible underlying causes are. It will be helpful first to define what is meant by obesity and then to look at how its occurrence has increased in recent years. Obesity is defined as having an abnormally high proportion of body fat and is predicated on body mass index (BMI), which is calculated using a simple formula based on height and weight: BMI = weight (in kilograms)/height (in meters) squared; or BMI = kg/m2. BMI can be calculated using pounds for weight and inches for height by using the conversion factor 704.5: BMI = 704.5 × weight (in pounds)/height (in inches)2. Some organizations, such as the American Dietetic Association, use 700 for the conversion factor, since BMI provides only a rough assessment of ideal body weight relative to overweight or obese body weight. The National Institutes of Health (NIH) adopted definitions for overweight and obesity in adults similar to those used by the World Health Organization (WHO): BMI between 25 and 30 is classified overweight, and BMI greater than 30 indicates obesity. There is also increasing concern regarding childhood obesity, although the federal government does not have a generally accepted definition for obesity in children and adolescents in terms of BMI. 14 Obesity Health Consequences and Dietary Influences 183 INFLUENCE OF DIET ON OVERALL HEALTH 184 National statistics for the United States indicate that the prevalence of overweight adults in the population changed very little from 1960 to 2000 (from 31.5 to 33.6 percent), whereas obesity more than doubled during that time period and now afflicts more than 30 percent of the adult population (WINNIDDK 2007). Extreme obesity, defined as a BMI greater than 40, increased nearly sixfold between 1960 and 2000 (from 0.8 to 4.7 percent of the adult population). The largest rate of increase occurred during the last decade of the twentieth century. It is generally agreed that obesity increases one’s risk of health problems. What this really means is that a greater proportion of obese people have health problems relative to the population whose body weight falls within the ideal range (BMI between 18 and 25). A few examples will serve to illustrate. Twothirds of the seventeen million people in the United States with type 2 diabetes have a BMI greater than 27, and nearly 50 percent have a BMI greater than 30 (WIN-NIDDK 2007). The prevalence of hypertension (systolic blood pressure greater than 140 and diastolic pressure greater than 90 mm Hg) is about 42 percent in obese men and about 38 percent in obese women. There is a strong correlation between blood pressure and BMI; as BMI increases, blood pressure tends to increase (see figure 14.1). Nearly half of postmenopausal women with breast cancer have a BMI greater than 29. Having a high BMI shortens one’s life expectancy by several years, with FIGURE 14.1. Relationship of body mass index (BMI) to hypertension (cystolic pressure > 140 and diastolic pressure > 90) and high blood cholesterol (> 240 mg/dL). Data from WIN-NIDDK 2007. 45 40 35 30 25 10 15 10 5 0 Hypertension High Blood Cholesterol Prevalence (%) Women Men Women Men BMI 30 [184.72.135.210] Project MUSE (2024-03-28 13:06 GMT) OBESITY 185 most of the increased risk of death at an earlier age coming from cardiovascular causes. It is interesting to note that high serum cholesterol levels are associated with being overweight and obese, but the prevalence of high cholesterol does not increase with BMI, as some other risk factors do (compare blood pressure, figure 14.1). The prevalence of high total serum cholesterol (greater than 240 mg/ dL) among obese individuals is 22 percent for men and 27 percent for women, and varies little for high overweight and low overweight categories (figure 14.1). In contrast, the prevalence of high cholesterol for those who are not overweight (BMI less than 25) is only about 13 percent for...