Obesity Part I: Epidemiology, Etiology and Pathophysiology, and Nonpharmacotherapeutic Treatments

The economist John Kenneth Galbraith wrote in the 1958 edition of The Affluent Society that “More people die in the United States of too much food than of too little” an observation that is even more fitting today than it was in the 1950’s. Nearly one third of adults in the United States are obese and the prevalence is increasing according to a recent report by the Institute of Medicine. 1 The prevalence of obesity increases with age for both men and women, but to a greater extent in women. The prevalence also is higher amongst Black and Hispanic persons, especially among women .2 Findings from the CDC’s Third National Health and Nutrition Examination Survey (NHANES III) revealed that 14% of children and 12% of adolescents were overweight. 3 DEFINITIONS OF OBESITY Obese: From Latin obesus, past participle of obedere (to devour) which derives from ob(meaning to) and edere (meaning eat) Websters New World Dictionary of the American Language, Second College Edition Although any one definition of obesity is apt to be incorrect, obesity is a chronic disease characterized by an excess of adipose tissue. It should be considered a serious medical condition that can lead to significant morbidity and mortality rather than a character flaw or personal weakness. In terms of size and girth, obesity is defined as a body mass index (BMI) of 27.8 or more for men and of 27.3 or more for women 1 which corresponds to about 20% above desirable weight according to the 1983 Metropolitan Life Insurance Company tables. For a man of average height (5’9”, 1.75 m) this translates to a weight greater than 85 kg (187 pounds) and for a woman of average height (5’4”, 1.63 m) a weight greater than 72 kg (158 pounds). The body mass index (BMI) is calculated by dividing the body weight (in kilograms) by the height (in meters) squared.1 Obesity is probably best defined as any degree of excess weight that imparts a health risk. Accordingly, the National Institute of Health issued new guidelines in 1995 that define healthy weight as a BMI less than 25. At this threshold an alarming 59% of Americans are obese. 1 CONSEQUENCES OF OBESITY Obesity, in combination with other risk factors, kills an estimated 300,000 Americans each year and it is the second most common cause of preventable deaths.4 Similar trends have been noted worldwide.5 Epidemiologic studies have revealed a clear association between obesity and the risks for cardiovascular disease, non-insulin dependent diabetes mellitus, certain forms of cancer, gallstones, some respiratory disorders, osteoarthritis, and an increase in overall mortality. 6 In addition to the amount of excess weight, the regional distribution of body fat contributes significantly to the risk for metabolic and cardiovascular disease. Upper body obesity (the “apple” shape, android, or central fat distribution) is characterized by a waist-to-hip girth ratio of greater than 0.85 and a subscapular skinfold thickness of greater than 25 mm. In contrast, lower body obesity (the “pear” shape, peripheral fat distribution) is characterized by a waist-to-hip girth ratio of less than 0.85 and a subscapular skinfold thickness of less than 25 mm. 7 The quartet of upper body obesity, hypertension, hypertriglyceridemia, and glucose intolerance is associated with an increased risk for Obesity Part I: Epidemiology, Etiology and Pathophysiology, and Nonpharmacotherapeutic Treatments 2 of 15 coronary heart disease, hypertension, and diabetes mellitus in both men and women. 7 These health risks appear to be mostly mediated by increased visceral intraabdominal fat, rather than subcutaneously distributed abdominal fat .6 The impact of obesity on social functioning and economic well-being can be as devastating as the medical consequences. Men who are obese are less likely to be married. Obese women not only marry less, but also complete fewer years of schooling and have lower incomes (and more have incomes below the poverty level).8 Much of this is attributed to discrimination against overweight persons.810 The economic costs of obesity are equally shocking. Epidemiologists at Harvard University estimated that the cost of treating obesity and the consequent diabetes, heart disease, hypertension, and gallstones exceeded an appalling $45.8 billion in 1990 accounting for 6.8% of total health care expenditures. 11 REGULATION OF BODY WEIGHT For land mammals, the ability to efficiently store food energy as fat provides a survival value when the food supply is scarce or sporadic.12 To maintain such food stores without undergoing continual alterations in size and shape, a system to maintain the balance between caloric intake and energy expenditure is necessary. It is increasingly apparent that the body has a highly complex and sophisticated system for regulating energy balance and fat stores. 13 The biology of this system is only beginning to be understood but pieces of the puzzle are falling into place. Some of these pieces are