Re: Does the stomach shrink as you get older??
The stomach is an expandable pouch.
It will stretch to accomodate a big meal, even permanently if a person frequently overfeeds. It will also shrink if not in use, sleeping or fasting. Hence why eating a very large meal in the morning will cause hunger to strike much earlier in the day and stronger, than drinking a liquid (ex..protein mix & fruit) shake for breakfast would.
This problem with your stomach could be caused by a multitude of things; stomach distension, bloating, weak abdominal wall etc. If the effect remains 2-3 hours after the first meal of the day than it is not your stomach, as by then your food would have been liquified, digested and in the intestines.