Hormone may help dieters keep weight off: U.S. study

By Julie Steenhuysen

CHICAGO (Reuters) - Falling levels of a hormone called leptin that helps the brain resist tempting foods may explain why people who lose weight often have a hard time keeping it off, U.S. researchers said on Friday.

Restoring leptin to pre-diet levels may reverse this problem, they said, offering a way for weary dieters to finally win the weight battle.

"When you lose weight you've created about the perfect storm for regaining weight," said Michael Rosenbaum of Columbia University Medical Center in New York, whose research appears in the Journal of Clinical Investigation.

After weight loss Rosenbaum said the metabolism not only becomes more efficient, so the body needs fewer calories, but the brain becomes more vulnerable to tasty-looking treats.

"Areas of your brain involved in telling you not to eat seem to be less active. You are more responsive to food and you are less in control of it," he said in a telephone interview.

Leptin is a natural appetite suppressant secreted by fat cells in the body. Its discovery created a stir in the 1990s when researchers found leptin caused mice to eat less and lose weight. This rarely happens in humans.

Since then researchers have been looking the best way to use the hormone to help treat obesity.

In earlier studies, researchers found that when people lose weight, leptin levels fall as the body tries to protect its energy stores.