The medical model of obesity treatment-combining diet, exercise, and behavior modification with antiobesity agents-suffered a setback when fenfluramine and dexfenfluramine were withdrawn from the market because of an association between these medications and valvular regurgitation. The Food and Drug Administration has recently approved sibutramine (Meridia), a norepinephrine and serotonin reuptake inhibitor that was originally developed as an antidepressant, but which has also been shown to reduce weight. Ln a 1-year placebo-controlled trial, 65% of patients receiving 15 mg sibutramine daily lost more than 5% of their body weight, compared with 29% of patients receiving a placebo; 39% of patients in the sibutramine group lost more than 10% of their body weight, compared with 8% of patients in the placebo group. Health benefits observed in patients receiving sibutramine include reductions in levels of triglycerides, uric acid, total cholesterol, and low-density lipoprotein (LDL) cholesterol and an increase in high-density lipoprotein (HDL) cholesterol levels. Another antiobesity drug currently under review by the Food and Drug Administration is orlistat (Xenical), a pancreatic lipase inhibitor that reduces the absorption of dietary fat by approximately 30%, thus reducing energy intake. In a 1-year placebo-controlled trial, 55% of patients receiving orlistat lost more than 5% of their body weight, and 25% lost more than 10% of their body weight, compared with 33% and 15%, respectively, of patients in the placebo group. Ln addition, orlistat slowed the rate of weight regain in the second year of treatment. Health benefits demonstrated in clinical trials of orlistat include reduced LDL cholesterol levels and increased levels of HDL cholesterol, reduced blood pressure and fasting insulin levels, improved oral glucose tolerance test outcomes, and improved glycemic control in obese patients with diabetes. The future of the pharmacologic treatment of obesity is promising. Many new antiobesity agents are in the early stages of development, and our understanding of the body's weight-regulating mechanisms is advancing steadily. Human trials of recombinant leptin are underway. Other promising compounds include those that block the Neuropeptide Y5 and Y1 (NY5, NY1) and Melanocortin-4 (MC4) receptors, stimulate uncoupling proteins, and unbind corticotrophin-releasing factor from its binding protein. As better medical treatments for obesity become available, the focus in dietary prescription may shift away from reducing energy intake toward healthier eating for disease prevention. At present, a comprehensive approach, which, in some patients, may include medical therapy as an adjunct, is necessary to treat obesity effectively.
