A study suggests that giving the hormone leptin to some fat people might help them slim down.
The study, reported in the February issue of the journal Nature Medicine, found the first direct evidence that people with low levels of leptin may be prone to weight gain.People who gained an average of 50 pounds over three years had started out with lower leptin levels than did people who didn't gain any weight, researchers found.
While the results don't prove low leptin levels lead to weight gain, they strongly suggest that, said Eric Ravussin, a visiting scientist at the National Institute of Diabetes and Digestive and Kidney Diseases.
The finding supports the idea that giving leptin might help some fat people slim down. Ravussin said some 10 percent of overweight people might be leptin-deficient.
Leptin made headlines in 1995 when scientists reported that it could melt weight off mice. It is made by fat cells and appears to tell the brain how much fat an animal is carrying.
The mouse brain is thought to have a leptin thermostat. If it senses a lot of leptin, which indicates a lot of fat, it tells the animal to eat less and be more active. If there's too little leptin, it signals the mouse to put on weight.
People have leptin in their blood too, but it's not clear whether it affects their weight. Studies of injecting leptin into people have already begun.
The results are intriguing, said John Foreyt of the Baylor College of Medicine in Houston, who also has studied leptin in people.
Foreyt said leptin isn't the only influence over a person's weight, nor would low levels necessarily mean a person will get fat.
"All of us are in control of our behavior," he said.