are people obese only because of overeating

Not exactly, the reason people are obese is due to overeating as well as having an inactive lifestyle. It's not just a matter of going on a diet. When some restrict their food intake too radically, they stop and return to overeating habits. Therefore it's a permanent lifestyle change that needs to be made for permanent results.

Over-eating is only one of the causes for obesity. As far as I know, there are genetic and hormonal disorders that cause obesity. I have noticed this also - some get obese with slight over-eating, but some others are heavy eaters but do not put on weight. I think the family tradition also has got a role in this matter. You may have noticed - all members of some families tend towards obesity while in some families all members are very lean. I myself was an example for poor eating but having overweight.

some people are obese from over eating an are not getting enough excerzise.many obese people may have health issue that causes them to gain weight.im not obese but i still need to lose a few pounds.even with my deit an excersizeing i still cannot lose the few pounds i wish to lose.i think it is cause by thyroid trouble an alot of people has thyroid troubles an not know it,so its hard to lose weight if you dont go to your dr for some advise.an make sure you do not have any health issue

Obesity is not only caused by over eating. There are some people who are obese because of a hormonal imbalance. I have friends who eat healthy and even exercise but are obese. Vice versa. I have some friends who eat a lot (and I mean a LOT) but are reed thin. I remember one tv personality who had to have one gland removed from her because that was what caused her to become overweight. (I forgot which gland though... sorry.)