Does your stomach shrink if you don't eat?

According to WebMD, the stomach does not change in dimension in adulthood, even if one reduces portion size and how often he eats. The main exceptions to this are surgical procedures such as gastric bypass surgery that physically modify the stomach's size.

Gastric bypass surgery, as WebMD states, involves stapling or removing a part of the stomach and connecting it to a part of the small intestine, vastly diminishing the capacity of the stomach and the calorie-absorbing capabilities of the small intestine. Over time, the effectiveness of the procedure may lessen if the stomach experiences pouch stretching, a gradual enlargement where the stomach eventually reaches its original size.