Obesity: an epidemic. (Editorial).

More than half of the adults in the United States today are either overweight or obese, compared with about 25% in the 1960s. (1,2) The prevalence of obesity increased by 5.6% between 2000 and 2001 alone. Obesity is associated with increased mortality risk, and statistics show the potential reduced life expectancy (4) and years of life lost (YLL) at various levels of increased body weight. (5) The body mass index (BMI), rather than just the body weight, should be taken into account. It can be calculated by one of the following equations:

BMI = body weight (in kg) / height in [in.sup.2] x 703

or

(Body weight in lbs / height in [in.sup.2]) X 703

The BMI associated with the least YLL, or greatest longevity, is 23 to 25 for whites and 23 to 30 for blacks. (5) For any degree of overweight, the YLL are greater in younger than in older adults.

In addition to its considerable psychological impact, obesity is associated with greater morbidity and poorer health-related quality of life than smoking, problem drinking, and poverty. (6) A BMI of 40 or more is associated with approximately a sevenfold increase in the risk of diabetes mellitus, a sixfold increase in the risk of hypertension, a fourfold increase in the risk of arthritis, a threefold increase in the risk of asthma, and a fourfold increase in the risk of having fair or poor health. (3) Obesity also is associated with increased risks for coronary heart disease, hyperlipidemia, gallstones, benign prostatic hyperplasia, and numerous types of cancer, including breast, endometrial, esophageal, gastric, colon, and renal cell carcinoma. A correlation between increasing BMI and decreasing physical function, vitality, and quality of life has been documented. (7,8) One of the most significant metabolic responses to obesity is insulin resistance, which in turn interferes with glucose and fat metabolism and results in an increase in free fatty acids and endothelial dysfunction. (9)

Although obesity is a polygenic disorder affected by a number of genes, and although a number of targets to treat obesity have been identified (eg, leptin, uncoupling proteins, peptide neurotransmitters regulating the balance between energy intake and energy expenditure), (10) the major cause of overweight and obesity is a mismatch between energy intake and energy expenditure, with the former exceeding the latter. Western civilization has evolved in such a way that energy intake has steadily increased while energy expenditure has steadily decreased. As civilization gradually has changed from hunting and gathering to agriculture to industry, the need to expend energy to survive has diminished considerably. People today absorb all of the calories they ingest, regardless of whether those calories are needed. Excess calories are stored as fat in the body for possible later use when food is not available.

Absorbing and storing as many calories as possible was essential for the survival of hunters when a steady supply of food could not be guaranteed. Farmers spent so much energy working the land that they, too, did not have reason to be concerned about excess nutritional intake. The situation today is different, however, and the mechanization of farming has reduced farmers' energy expenditure. Even in industry, the automation of various heavy processes has reduced significantly the amount of physical exercise during the workday.

It is sobering to reflect on the various gadgets available to make life more comfortable. Remote controls allow one to change television, radio, or videocassette programs with the flick of a finger, without the need to get up from one's armchair; email is replacing the need to mail letters or to go to someone's office to deliver a message; cellular telephones allow people to avoid the need to rush to answer a ringing stationary telephone. Even warming one's house or preparing a meal nowadays is a relatively sedate, low-energy exercise, and brushing one's teeth demands less exertion if an electric toothbrush is used.

At the same time that the need to expend energy has decreased, the opportunities to increase energy intake have increased substantially. High-calorie, high-fat fast-food outlets are available at practically every street corner. "Super" size meals are available at a bargain price. One can almost double one's calorie intake at the cost of only a few more pence! What a temptation to a cost-conscious society! And what about all the delicious but, alas, high-sugar, high-fat snacks that are available?

It is ironic that the same century that saw the discovery and subsequent conquest of scurvy, pellagra, and various nutritional deficiencies also witnessed the increased prevalence of overweight and obesity. If the present rate of increase in the prevalence of overweight and obesity continues, obesity is likely to replace cigarette smoking as the primary preventable cause of death in the United States. (11) It is even more ironic that obesity is more prevalent among the lower socioeconomic classes and is becoming more prevalent in developing and underdeveloped nations where cigarette smoking, malnutrition, parasitic infestations, and infectious disease are still major health hazards. Obesity is a largely preventable disease. It can and should be prevented.

References

(1.) Flegal KM, Carroll MD, Ogden CL, Johnson CL. Prevalence and Wends in obesity among US adults, 1999-2000. JAMA 2002;288:1723-1727.

(2.) Kuczmarski RJ, Flegal KM, Campbell SM, Johnson CL. Increasing prevalence of overweight among US adults: The National Health and Nutrition Examination Surveys, 1960 to 1991. JAMA 1994;272:205-211.

(3.) Mokdad AH, Ford ES, Bowman BA, Dietz WH, Vinicor F, Bales VS, et al. Prevalence of obesity, diabetes, and obesity-related health risk factors, 2001. JAMA 2003;289:76-79.

(4.) Peeters A, Barendregt JJ, Willekens F, Mackenbach JP, Al Mamun A, Bonneux L. Obesity in adulthood and its consequences for life expectancy: A life-table analysis. Ann Intern Med 2003;138:24-32.

(5.) Fontaine KR, Redden DT, Wang C, Westfall AO, Allison DB. Years of life lost due to obesity. JAMA 2003;289:187-193.

(6.) Sturm R, Wells KB. Does obesity contribute as much to morbidity as poverty or smoking? Public Health 2001;115:229-235.

(7.) Fine JT, Colditz GA, Coakley EH, Moseley G, Manson JE, Willett WC, et al. A prospective study of weight change and health-related quality of life in women. JAMA 1999;282:2136-2142.

(8.) Coakley EH, Kawachi I, Manson JE, Speizer FE, Willet WC, Colditz GA. Lower levels of physical functioning are associated with higher body weight among middle-aged and older women. Int J Obes Relat Metab Disord 1998;22:958-965.

(9.) Steinberg HO, Gumbiner B. Pathophysiology of obesity and metabolic response to weight loss, in Gumbiner B (ed): Obesity. Philadelphia, American College of Physicians, 2001, ed 3, pp 50-66.

(10.) Williams LB. Considine RV. Etiology of obesity, in Gumbiner B (ed): Obesity. Philadelphia, American College of Physicians, 2001, ed 3, pp 23-49.

(11.) Allison DB, Fontaine KR, Manson JE, Stevens J, Vanltallie TB. Annual deaths attributable to obesity in the United States. JAMA 1999;282: 1530-1538.