I don't think I mentioned this but I am not certain. If not, it's amazing because I observed this very key phenomenon way back in 1986.
Your interest in, cravings for or temptation to eat junk food is inversely proportional to your current fitness.
When I am busy and schedule challenged I get into the mood for candy and what not. When I am in shape to compete in a 5k race, I have no desire for such things.
And I don't sit and sit and eat big meals.
Purely out of want - no concious effort required.
So while exercise will burn carbs and calories and lower cholesterol and improve your general health and metabolism, the single biggest benefit it gives you in losing weight or reversing Syndrome X is the thing it does to your appetite. It replaces your appetite for junk food with an appetite for lite.