Obesity

Obesity , defined as a body mass index of 30 or greater, is an epidemic in the United States and other industrialized nations, and it is rapidly becoming one in developing nations. As countries transition to westernized lifestyles, obesity tends to increase. Obesity rates vary from as little as 2 percent in some Asian countries to as much as 75 percent in some Pacific nations. There are more than 300 million obese persons in the world, and more than 750 million overweight persons. In the United States, 34 percent of adults are over-weight and 30.5 percent are obese. Between 1980 and 2000, the percentage of overweight children ages six to eleven doubled, from 7 percent to 15 percent, and the percentage of overweight adolescents ages twelve to nineteen tripled, from 5 percent to 16 percent (Ogden, et al.). In Europe, the thinnest country is Sweden, with about 10 percent obesity, while the fattest is Lithuania, with about 79 percent obesity. The sad fact is the prevalence of obesity appears to be increasing in all countries.

An obese person has a 50 to 100 percent increased risk of premature death compared to someone of normal weight. In the United States, more than 300,000 deaths a year are attributable to obesity. Obesity is associated with type 2 diabetes , coronary heart disease , stroke , hypertension , elevated blood cholesterol , some cancers (e.g., colon, endometrial, kidney, gallbladder, and postmenopausal breast cancer ), osteoarthritis , gallbladder disease, and respiratory disease. In addition, obesity is often associated with discrimination and prejudice, causing some obese people to suffer poor self-esteem and reduced quality of life. The health care costs attributable to obesity exceed $100 billion a year in the United States, more than 6 percent of the total health care costs.

What Causes Obesity?

Obesity is caused by many factors. A person's weight is determined by a combination of genes , metabolism , behavior, culture, and environment . Genes and metabolism may help explain about 25 to 40 percent of body weight. However, a person's environment overwhelms the minor influences of biology. While genes may increase one's risk for obesity, they do not by themselves cause obesity. Genes certainly can't explain the rapidly increasing prevalence of obesity around the world.

For most people, obesity results from eating too much and not being active enough. The overwhelming factors responsible for obesity are environmental. Modern Western society encourages poor diets and lack of exercise. For example, portion sizes continue to increase. Americans were eating about 200 more calories per day in 2003 than they were in 1993. Fast-food restaurants encourage customers to "super size" and purchase "value" meals. Many target children, using well-known movie stars and cartoon characters in their advertising. Further, people eat out more often than in the past and many restaurants offer huge portion sizes. Americans seem determined to get as much food as they can for their money.

Television contributes to obesity through commercials urging people to buy food of low nutritional value, and by encouraging sedentary behavior. Many people tend to snack while watching television. Americans simply don't get enough physical activity. Less than one-third of American adults report that they do at least thirty minutes of brisk walking or other moderate activity on most days of the week, and almost half do no leisure-time activity at all. Almost half of U.S. high school students watch television more than two hours every day. This lack of physical activity is contributing to the increases in obesity and to other health-related conditions.

Treatment of Obesity

Weight loss in obese persons improves health. Weight losses of ten to twenty pounds have been shown to lower blood pressure , blood cholesterol, and blood glucose (in persons with type 2 diabetes), and to improve other health problems. An obese person does not have to lose fifty or a hundred pounds to realize health benefits, however, for even modest losses of weight can lead to major health benefits.

Diets

Reducing calories is one requirement for weight loss. Cutting only 100 extra calories a day from one's diet will lead to a weight loss of 10 pounds in a year, while cutting 500 calories a day will lead to a loss of 50 pounds in a year. Most health organizations recommend a specific distribution of calories.

For example, about 25 to 30 percent of total calories should be from fat (mainly unsaturated fat, such as olive oil, corn oil, and safflower oil), 15 percent from protein , and 50 to 60 percent from carbohydrates (mainly complex carbohydrates, such as fruits and vegetables). Recommended total calories should be based on height, weight, age, and activity level. A plant-based diet, consisting of an abundance of fresh vegetables and fruit and limited in calories, seems to be a healthful one for most people.

Physical Activity

Burning only an extra 100 calories a day by walking briskly for about 20 minutes will lead to a weight loss of about 10 pounds a year, while burning an extra 300 calories by walking briskly for about 60 minutes a day will lead to a weight loss of about 30 pounds. Physical activity contributes to weight loss, decreases abdominal fat, increases cardiorespiratory fitness, and helps with maintenance of lost weight. Any aerobic exercise, such as swimming, bicycling, jogging, skiing, or dancing, leads to these benefits, but for most obese people brisk walking seems to be the easiest activity to do. Other forms of exercise, such as resistance training or lifting weights, can also be helpful in a weight loss program. Finding ways to be more active every day, such as walking up a flight of stairs rather than taking the elevator, or walking somewhere rather than driving, can help a person burn calories without much effort.

Combined Diet and Exercise

The combination of a reduced-calorie diet and increased physical activity will lead to better weight loss than either one done separately. Small changes in diet and physical activity done each day is the key to long-term, successful weight loss for most obese people.

SEE ALSO Body Image ; Body Mass Index ; Childhood Obesity ; Fad Diets ; Fast Foods ; Overweight ; Weight Loss Diets ; Weight Management .

John P. Foreyt

Bibliography

Flegal, Katherine M.; Carroll, Margaret D.; Ogden, Cynthia L.; and Johnson, Clifford L. (2002). "Prevalence and Trends in Obesity among U.S. Adults, 1999–2000." Journal of the American Medical Association 288(14):1723–1727.

Foreyt, John P.; McInnis, Kyle J.; Poston, Walker S. C.; and Rippe, James M.; eds. (2003). Lifestyle Obesity Management. Malden, MA: Blackwell.

Ogden, Cynthia L.; Flegal, Katherine M.; Carroll, Margaret D.; and Johnson, Clifford L. (2002). "Prevalence and Trends in Overweight among U.S. Children and Ado lescents, 1999–2000." Journal of the American Medical Association 288(14):1728–1732.

Poston, Walker S. C., and Foreyt, John P. (1999). "Obesity Is an Environmental Issue." Atherosclerosis 146:201–209.