Hormone fights fat in humans.

Leptin, the so-called obesity hormone, may help overweight people trim unwanted body fat, according to a new study.

Previous research has shown that injections of leptin helped obese mice slim down (SN: 7/29/95, p. 68). But would this hormone do the same for overweight people?

Andrew S. Greenberg, an obesity researcher at Tufts University and the New England Medical Center in Boston, and his colleagues decided to find out. The team recruited 70 moderately obese people, dividing them into five groups. Four groups received daily injections of leptin at different dosages, while the last group got inactive, or placebo, injections.

The researchers also put the study participants on a diet that provided them with 500 fewer calories than their estimated daily energy needs. Only 46 of the participants stayed with the study for its full 6-month duration.

The 10 obese people who got the highest leptin dose (0.3 milligrams per day per kilogram of body weight) lost an average of 16 pounds in the 6 months, Greenberg reported in June at the American Diabetes Association meeting in Chicago.

The response to leptin varied greatly from person to person. One member of the high-dosage group actually gained weight while being treated; another lost more than 35 pounds, Greenberg says.

Those individuals receiving a placebo lost an average of 4 pounds, he adds.

The study was too small to answer the question of whether leptin will provide a useful treatment for obesity, Greenberg told Science News. The study, however, did indicate that injections of leptin are safe. The participants in this trial reported only minor side effects, such as redness of the skin.