Obesity Hormone Drops
with Diet and Exercise

NEW YORK (Reuters Health) - It is no mystery that eating a healthy diet and exercising can make extra pounds disappear. But the results of a new study suggest that lifestyle changes may also lower levels of leptin, the ``obesity hormone'' thought to be involved in appetite regulation.

Fat cells and other tissues in the body produce leptin, which is believed to notify the brain to reduce appetite when fat cells are ``full.'' Exactly how the hormone works to control appetite is uncertain, however.

To see what effect weight loss has on leptin levels, Dr. Janne E. Reseland of the University of Oslo in Norway and colleagues followed 186 men with moderately high blood pressure and cholesterol levels who made lifestyle changes. A ``control'' group of men did not change their diet or begin exercising. Others were randomly assigned to adopt a reduced-calorie diet, to begin an exercise program, or to combine both lifestyle changes.

Not surprisingly, exercise, a healthy diet or a combination of the two led to weight loss, including a reduction in body fat, during the one-year study. The investigators also found that leptin levels declined significantly in men who made changes in diet, exercise or both. The findings are published in the American Journal of Clinical Nutrition.

But when the researchers took into account the amount of fat lost during the study, they found that leptin levels dropped more than expected.

``We conclude that long-term diet and exercise interventions may have direct effects on the plasma leptin concentration beyond the effect expected due to changes in fat mass,'' the authors conclude.

One interpretation of the findings, Reseland told Reuters Health, is that long-term reductions in leptin levels may somehow adjust the way the central nervous system regulates appetite and metabolism. This adjustment may help maintain weight loss in the long run, according to Reseland.

Since some researchers had hoped that giving people leptin might encourage weight loss, it may seem odd that the current study found that leptin levels decreased with weight loss. However, past studies have found that people who are obese do not lack the hormone, they actually have higher-than-normal levels.

The researchers do not have a firm answer to these questions, but according to Reseland, overweight individuals may develop a resistance to leptin, meaning that their bodies become less responsive to the hormone's appetite-regulating messages.

SOURCE: American Journal of Clinical Nutrition 2001;73:240-245.
Reference Source 89

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