Stress Unlocks Fat Cells, Ups Obesity

July 2, 2007 -- Stress may stimulate obesity by unlocking the body's fat cells, a new study suggests.

Researchers found a molecule the body releases when stressed called NPY (neuropeptide Y). NPY appears to unlock certain receptors in fat cells, causing them to grow in both size and number.

But the good news is that by blocking those Y2 receptors, researchers say they may be able to eventually develop new drugs to combat stress-related obesity.

"We have known for over a decade that there is a connection between chronic stress and obesity," Herbert Herzog, PhD, of the Garvan Institute of Medical Research in Sydney, Australia, says in a news release. "We also know that NPY plays a major role in other chronic stress-induced conditions, such as susceptibility to infection. Now we have identified the exact pathway, or chain of molecular events, that links chronic stress with obesity."

Stopping Stress From Turning to Fat

In the first part of the study, published in Nature Medicine, researchers fed stressed and unstressed mice either a standard diet or a high-fat, high-sugar, "comfort food" diet.

As expected, the mice on the high-fat, high-sugar diet gained fat while those on the standard diet did not. But researchers found the stressed mice on the high-fat, high-sugar diet developed more body fat than the unstressed mice fed the same diet.

Those results prompted researchers to look for differences in how the stressed mice utilized and stored fat.

"There is not much we can do about the increased levels of NPY caused by stress, but we can do something about the damage it causes," says Herzog.

They found that when they blocked the Y2 receptors for two weeks, the stressed mice lowered their abdominal fat deposits by 40%.

"Even more surprisingly, in addition to having flatter bellies, adverse metabolic changes linked to stress and diet, which include glucose intolerance and fatty liver, became markedly reduced. We do not know yet exactly how that happens, but the effect was remarkable," researcher Zofia Zukowska of Georgetown University says in the release. "Our findings suggest that we may be able to reverse or prevent obesity caused by stress and diet, including the worst kind of obesity; the apple-shaped type, which makes people more susceptible to heart disease and diabetes."

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