Although certain fruits like grapes can cause a gas that sometimes leads to a bloated feeling, grapes do not exclusively expand your stomach when you eat them. The fact of the matter is that eating enough of any food can expand your stomach and cause you to feel quite bloated. While grapes may not expand your stomach, they do require extra fluids and saliva in order to digest properly.
Improper digestion of grapes can sometimes lead to stomach cramps, which is most likely where this myth originated from. After eating enough grapes anyone’s stomach can expand but this is true when you consume any food.