It all depends on the person. I know somebody who was born fat. She's now in her 60s, and she's absolutely astronomical. Sometimes, it isn't all down to eating too much/poor exercise; it is sometimes down to just the way the individual person is. Which is why I get cross at people who are so judgmental, and deem being fat on eating too much/lack of exercise.
That wasn't aimed at anyone in this thread, by the way.