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How they affect your appetite and your weight

If there was a hormone in your body whose chief job was to make you feel hungry, most of us probably wouldn't be too keen on it. (I don't know about you, but having a healthy appetite has never been a problem for me.) But if there was a hormone that decreased our appetites, we'd order buckets of it!

Well, let me introduce you to some hormones that do just those things: the "hunger hormones," leptin and ghrelin.

Leptin is a hormone, made by fat cells, that decreases your appetite. Ghrelin is a hormone that increases appetite, and also plays a role in body weight.

Levels of leptin -- the appetite suppressor -- are lower when you're thin and higher when you're fat. But many obese people have built up a resistance to the appetite-suppressing effects of leptin, says obesity expert Mary Dallman, PhD, from University of California at San Francisco.

Here's what we know so far about the "hunger hormones" and what we can do to help control our appetites.

What We Know About Ghrelin

Ghrelin, the appetite increaser, is released primarily in the stomach and is thought to signal hunger to the brain. You'd expect the body to increase ghrelin if a person is undereating and decrease it if he or she is overeating. Sure enough, ghrelin levels have been found to increase in children with anorexia nervosa and decrease in children who are obese.

German researchers have suggested that ghrelin levels play a big role in determining how quickly hunger comes back after we eat. Normally, ghrelin levels go up dramatically before you eat; this signals hunger. They then go down for about three hours after the meal.

But some researchers believe that ghrelin is not as important in determining appetite as once thought. They think that its role in regulating body weight may actually be a more complex process.

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