In the past it was thought that bodyfat was just inert tissue, a stored energy source. Now scientists know that fat can produce substances that damage health and make you fatter. For example, new research shows that abdominal fat produces neuropeptide Y, a hormone that makes you hungry. It’s a vicious circle, as the more fat you put on, the hungrier you get. There’s one more reason to whittle your middle—lower grocery bills.