When used as directed in a comprehensive, physician-supervised weight loss program that includes a low-fat diet and regular exercise, Prozac can increase weight loss by about an additional 10 percent. However, weight loss may not be permanent, especially after this drug is discontinued.

Prozac is an antidepressant, the best-known member of the chemical family of drugs called selective serotonin reuptake inhibitors (SSRI's). It is FDA approved for treatment of depression, bulimia, and obsessive-compulsive disorder. It is not specifically approved for weight loss, but doctors may prescribe approved medications for unapproved uses.

The typical dose is 60 mg a day.

It is not entirely clear why Prozac helps people lose weight. It may limit appetite. It may also raise the rate at which the body burns calories. And because some people overeat when depressed, its antidepressant action may reduce food consumption.

In one study, a large group of obese adults was divided into two groups. Half took Prozac (60 mg/day) while half took a placebo. After 28 weeks, the Prozac group lost significantly more weight. But they regained it after discontinuing the drug.

Side effects included: fatigue, diarrhea, sweating, insomnia, thirst, nausea, and vomiting.