The stomach will expand to fit a gallon of ice cream, but that doesn't mean it should. The best measurement is your hands. You shouldn't eat more at one sitting than would fit in two hands cupped together. Also, increase your in-take of fresh fruits and vegetables to seven servings a day and, if you consume red meat, eat it no more than twice a week. These subtle changes will decrease acid reflux, constipation, and indigestion.