Erm, simple, if you dont want to get so fat, dont eat so much. The more exercise you do in ratio to eating, the fitter you're likely to get.
I eat like an absolute pig with LOADS of sweets, chocolate, fry ups, sandwiches, normal dinner, 4 bowls of whatever for breakfast... and im thin as a rake. I go out on my bike loads, walk to towm every now and then, go swimming 2 or 3 times a week...