overweight and underweight

1. It is beacause some people sometimes eat many things and they have no balanced diet, they don't eat vegetables and drink more water, they only eat some have fat and unhealthy food so they will overweight.

2. ( underweight.) It is beacuse they don't eat things and healthy food.
Or some people afraid they will very fat and don't want to them be very fat, so they don't eat much food (breakfast.etc.) Then they will underweight.

If people eat too much and eat a lot of oily or junk food then they will overweight
on the other hand
people who didn't eat a lot, and the meal time always change, then something they will underweight