Study suggests hormone leptin may have larger role in obesity

Treatment with leptin, a natural hormone that helps control body weight, could help many fat people slim down, even if they already have some in their bodies, a new study suggests.

Leptin treatment has already helped people who completely lack the hormone because of a genetic mutation. But only a handful of people don't have any leptin at all naturally.

Results of treatment with other obese people have been disappointing, with only some subjects losing small amounts of weight.

The new work didn't involve treatment. Instead, research-ers studied 13 people who had only about half the normal level of leptin because of a genetic glitch. They found that three-quarters of this group was obese, compared to just one-quarter of a comparison group.

That shows that even in people who have some leptin, the amount still affects weight, the researchers said.

"People have been saying it doesn't matter how much leptin you have as long as you have a smidgen. Our research suggests that it does matter," said Stephen O'Rahilly of the University of Cambridge, England.

So the work suggests that leptin treatment can help not only those very rare fat people who completely lack the hormone, but also those with low levels, O'Rahilly and his colleagues conclude in the Nov. 1 issue of the journal Nature.

Some experts said it's not clear how many obese people have low leptin levels, although one estimated it could be about 25 percent.

Discovered in 1994, leptin is normally produced by fat cells and is believed to provide a signal about the amount of body fat to the body's energy-regulation system.