If you gobble up so much lasagna or so many slices of birthday cake that your stomach hurts, you overeat, or consume too much.
When people eat too much food, more than they need or are hungry for, they overeat. If you overeat regularly for a long time, you'll gain extra weight. One indulgent night of overeating may simply give you terrible indigestion and the desire to never see another hot dog in your life. We've used this verb, which comes from the Old English oferæt, "gluttony," since the 1590s.