Thus, if they overeat or eat something poisonous, vomiting is not an option. Rather, we might under-eat or overeat depending on the company we are in. When people overeat, their bodies have the tendency to chemically change, including metabolic shifts. The tendency is to overeat after a fast, but this should be avoided. Feelings of depression can cause a child to overeat. For example, many people overeat during festivals or while on holiday.