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Chapter: Medical Physiology: Dietary Balances; Regulation of Feeding; Obesity and Starvation; Vitamins and Minerals

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Treatment of Obesity

Treatment of obesity depends on decreasing energy input below energy expenditure and creating a sus-tained negative energy balance until the desired weight loss is achieved.

Treatment of Obesity

Treatment of obesity depends on decreasing energy input below energy expenditure and creating a sus-tained negative energy balance until the desired weight loss is achieved. In other words, this means either reduc-ing energy intake or increasing energy expenditure. The current National Institutes of Health (NIH) guidelines recommend a decrease in caloric intake of 500 kilo-calories per day for overweight and moderately obese persons (BMI greater than 25 but less than 35 kg/m2) to achieve a weight loss of approximately 1 pound each week. A more aggressive energy deficit of 500 to 1000 kilocalories per day is recommended for persons with BMIs greater than 35 kg/m2. Typically, such an energy deficit, if it can be achieved and sustained, will cause a weight loss of about 1 to 2 pounds per week, or about a 10 per cent weight loss after 6 months. For most people attempting to lose weight, increasing physical activity is also an important component of successful long-term weight loss.

To decrease energy intake, most reducing diets are designed to contain large quantities of “bulk,” which is generally made up of non-nutritive cellulose substances. This bulk distends the stomach and thereby partially appeases hunger. In most lower animals, such a proce-dure simply makes the animal increase its food intake even more, but human beings can often fool themselves because their food intake is sometimes controlled as much by habit as by hunger. As pointed out later in con-nection with starvation, it is important to prevent vitamin deficiencies during the dieting period.

Various drugs for decreasing the degree of hunger have been used in the treatment of obesity. The most widely used drugs are amphetamines (or amphetamine derivatives), which directly inhibit the feeding centers in the brain. One drug for treating obesity is sibu-tramine, a sympathomimetic that reduces food intakeand increases energy expenditure. The danger in using these drugs is that they simultaneously overexcite the central nervous system, making the person nervous and elevating the blood pressure. Also, a person soon adapts to the drug, so that weight reduction is usually no greater than 5 to 10 per cent.

Another group of drugs works by altering lipid metabolism. For example, orlistat, a lipase inhibitor,reduces the intestinal digestion of fat. This causes aportion of the ingested fat to be lost in the feces and therefore reduces energy absorption. However, fecal fat loss may cause unpleasant gastrointestinal side effects, as well as loss of fat-soluble vitamins in the feces.

Significant weight loss can be achieved in many obese persons with increased physical activity. The more exercise one gets, the greater the daily energy expendi-ture and the more rapidly the obesity disappears. Therefore, forced exercise is often an essential part of treatment. The current clinical guidelines for the treat-ment of obesity recommend that the first step be lifestyle modifications that include increased physical activity combined with a reduction in caloric intake. For morbidly obese patients with BMIs greater than 40, or for patients with BMIs greater than 35 and conditions such as hypertension or type II diabetes that predispose them to other serious diseases, various surgical proce-dures can be used to decrease the fat mass of the body or to decrease the amount of food that can be eaten at each meal.

Two of the most common surgical procedures used in the United States to treat morbid obesity are gastric bypass surgery and gastric banding surgery. Gastricbypass surgery involves construction of a small pouch inthe proximal part of the stomach that is then connected to the jejunum with a section of small bowel of varying lengths; the pouch is separated from the remaining part of the stomach with staples. Gastric banding surgery involves placing an adjustable band around the stomach near its upper end; this also creates a small stomach pouch that restricts the amount of food that can be eaten at each meal. Although these surgical procedures generally produce substantial weight loss in obese patients, they are major operations, and their long-term effects on overall health and mortality are still uncertain.


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