[SiVal]

No, it's that people who exercise more tend to eat more, even when their primary reason for exercising is to lose weight. They either don't think about it or overestimate the calories burned by their exercise and allow themselves to eat a bit more, mistakenly believing that the net result is still negative calories.

Moderate exercise is good for you whether or not you want to lose weight, but if weight control is one objective, you need to be more careful than most people realize to avoid eating more when you exercise more.