Why do people get cramps?

People get cramps when they eat then exercise. Because of the reactivity to your food digesting and exercising, your brain sends out messages to your body that cramp it. This should make you slow down and digest your food. Well most of the time when you dont eat all junk food. im not trying to manage your life but those of you that eat junk food dont eat alot of those i do myself but not that much you can lose weight just lay off those chips andstuff for a while.