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 appe...