Intentional weight loss is a reduction of the total body mass that occurs when you burn more calories that you take in.
Many dietary strategies have been designed to help lose excess weight. Among the first agents to be used for weight loss were thyroid hormone and digoxin, with disappointing results.
Most currently available weight loss agents are FDA approved for short term use up to 3 months. Sibutramine (Meridia) and orlistat (Xenical) are approved for long term use in patients who are significantly obese. However, their safety and effectiveness have not been established for use beyond 2 years.
Weight loss agents promote an average loss of 5 to 20 pounds. Some persons lose more than 10 percent of their initial body weight. Maximum weight loss usually occurs within 6 months of starting the treatment. Weight then tends to level off or increase gradually during the remainder of treatment.
Weight loss agents should be used only by patients who are at increased medical risk because of their weight. They are approved only for those with a body mass index (BMI) of 30 and above, or 27 and above if they have obesity-related conditions, such as high blood pressure, dyslipidemia (abnormal amounts of fat in the blood), or type 2 diabetes. A BMI of 18.5 to 24.9 is considered healthy.
Orlistat (Xenical) acts in a quite different way from popular appetite suppressants. It inhibits the absorption of fat from the intestine and instead of being absorbed into the body, it is excreted in the stool. Since fat is excreted rather than absorbed, caloric and fat intake is reduced.
Orlistat blocks absorption of around 30% of ingested dietary fat. People taking it may expect to reduce body weight by an average of 10%. Side effects are confined to the gastrointestinal tract, are minor and short term and are regulated by diet.
Appetite suppressants (Anorectics)
Appetite suppressants (anorexiants) promote weight loss by decreasing appetite or increasing the feeling of being full. Appetite suppressants make you feel less hungry by increasing one or more brain chemicals that affect mood and appetite. Phentermine (Adipex, Ionamin) and sibutramine (Meridia) are the most widely used appetite suppressants in the U.S.
Their appetite reducing effect tends to decrease after a few weeks, and so they are useful only during the first few weeks and can help you to lose weight while you are making changes in diet and lifestyle.
Phentermine (Adipex-P, Fastin, Ionamin, Zantryl) was approved by the FDA in 1959 for short-term treatment of obesity.
Diethylpropion (Tenuate, Tenuate Dospan), like phentermine, is approved only for short-term treatment of obesity.
Benzphetamine (Didrex) is less commonly used anti-obesity anorexiant.
Sirbutamine (Meridia) was approved by the FDA in 1997. Sibutramine enhances satiety by increasing the activity of brain chemicals called norepinephrine and serotonin. It has been approved by the FDA for weight loss and the maintenance of weight when combined with a reduced-calorie diet.
Sibutramine may also improve lipid balance in people with high blood cholesterol levels and improve glycemic control in people with type 2 diabetes.