Health & Medical Diet & Fitness

Blood Fats Linked to Appetite, Obesity

´╗┐Blood Fats Linked to Appetite, Obesity

Blood Fats Linked to Appetite, Obesity

Fats Block 'Stop Eating' Signal to Brain; Fat-Lowering Drug May Help

April 27, 2004 -- What causes obesity? Blame blood fats, a new study suggests.

Your body has a very effective way to keep you slim: It tells you to stop eating. It does this by sending out a chemical signal -- a hormone called leptin. When leptin reaches the brain, your brain says, "Enough." Hunger goes away.

But high levels of blood fats -- technically, triglycerides -- block this signal before it gets to the brain, report William A. Banks, MD, of the VA Medical Center in St. Louis and Saint Louis University, and colleagues. This is the cause of obesity, they suggest in the May issue of Diabetes.

"We figured out how obesity occurs," Banks says in a news release. "This is a big deal. We now know what is keeping leptin from getting to where it needs to go to do its work."

Evolution and Modern Man

Starvation -- not obesity -- was our ancestors' main problem during most of evolution. That explains why the body has a built-in system for keeping its hunger switch in the "on" position.

When a person badly needs food, levels of blood fats get high. This blocks leptin and keeps a person hungry and looking for food.

Unfortunately, having plenty to eat causes a new problem -- one for which we haven't yet evolved a natural solution. Obese bodies also have a lot of fats in the blood. This, too, keeps a person hungry and looking for food.

"We feel that we now understand what part of the system is broken -- why leptin isn't working," Banks says. "We have a better understanding of why people are becoming obese."

Fighting the Cause of Obesity

In their experiments, Banks' research team showed that triglycerides do indeed keep leptin out of the brains of obese mice. The more triglyceride fats they ate, the less leptin reached their brains. Vegetable triglycerides did not block leptin, but animal triglycerides did.

A triglyceride-lowering drug -- Lopid -- reversed this leptin-blocking effect in the obese mice. Such treatments might work in humans, suggests John Morley, MD, director of geriatric medicine at Saint Louis University and a member of Banks' research team.

"If you lower triglycerides, you should theoretically help the body's own leptin to work better so people can get skinnier," Morley says in a news release.

Eating a low-fat diet is a natural way to lower your blood fats. It's not clear that Lopid or other drugs will help, but much more study is needed before such treatments can be used to treat obesity.

And even if Lopid did work this wonder, it's no magic potion. A person taking the drug has to be on a low-fat diet.

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