Why do people eat too much?

If you eat too much, compared to your physical activity, you will gain weight and in the extreme you will get fat. Political Correctness notwithstanding, most people recognize that being fat is unhealthy and generally regarded as unattractive, plus there is a not so subtle negative moral judgement cast toward fat folks. Being unhealthy, being unattractive, and being subjected to a distinct social antipathy to fatness, is a burden that most people would choose to avoid. Since avoiding this issue is, in most cases, a matter of eating less, why do people eat too much? Most reasonable people want to be healthy, attractive and socially acceptable. And although lots of people exercise, most do not exercise too much. But many people eat too much. So why is extreme exercise regarded with skepticism, but extreme eating is regarded as no big deal?