It seems like some people dismiss outright any link between exercise and weight loss, or the body's regulation of weight. Here's an article with some interesting findings and possible explanations.
From the article "Another possible explanation relates to appetite. At high levels of exercise, numerous studies have found that appetite tends to closely match energy requirements. But this relationship breaks down at lower levels of exercise. If you feed someone a 200-calorie snack early in the day, for example, heavy exercisers will unconsciously adjust their appetite to eat 200 fewer calories over the rest of the day. Sedentary subjects, on the other hand, will eat just as much as they normally would have."