Having big belly can be genetically inherited and is not necessarily a result of over eating.
We do not have in Islam any criticism of men or women with big bellies, but we do have criticism of over eating. (Human being did not fill a vessel more harmful for him than his stomach) is just one example of Hadeeths in this regard.
We have Hadeeths encouraging eating less, speaking less, and sleeping less as a way of healthy life. Less here means avoiding over eating, over speaking, and over sleeping.