You might eat more after you exercise because exercise can make you hungry. It doesn’t have to, but it can. You also might eat more after you exercise, not from hunger, but because you feel you deserve a reward for exercising. Just think, if you didn’t change your old weight-gaining and weight-maintaining eating habits what you might want to reward yourself with. It might be those old chips. Never get enough of them. Or a sweet. You deserve a sweet, don’t you—for sweating through that workout.
There is still another possibility besides eating that can lead to wiping away all your hard work exercising. You will probably be tired from your workout and you will most likely rest more than usual, which means you won’t be expending the same amount of energy you usually do when you are not exercising.
Don’t forget this cautionary wisdom when someone holds up exercise to you as the elixir for weight loss.