There's nothing that controls our desire for food, but there is a control center in our brain that monitors it. The appestat, a control center for food intake, is located in our hypothalmus. The appestat functions like a food thermometer. It turns on eating behavior and then turns it off when the desire or hunger has been satisfied. Unfortunately, the appestat gets its information from the bloodstream, and it takes several minutes for the food nutrients to enter the bloodstream and for the message to be received.
Physiological factors affect the appestat, too.
Low blood sugar, hormone imbalances, cold temperatures, hunger pangs from an empty stomach and unfilled fat cells also stimulate it. Studies have shown that regular physical activity helps the appestat adjust caloric intake to energy needs. Finally, choosing to exercise before or after a meal can positively affect postprandial lipemia - the presence of fat in the blood. Research done at the University of Florida showed that exercise before or after a meal reduced the magnitude and duration of postprandial lipemia. And more good news - mild exercise proved just as beneficial as strenuous.