I heard something on NPR today that the American diet has tons more sugar in it than it used to 40 years ago. The excess sugar spikes your insulin, which means many of your calories go immediately into fat. The problem is, you actually need those calories to power your energy needs, so you eat more. If you don't eat more, you feel like you're starving. You're cranky and have no energy to do anything, including exercise. But anything you eat, you still only get part of the calories of. The extra insulin is like a "tax" on your calories, like the government taking 20% out of your paycheck before you even see it. Like government, it goes to fat.
So their advice was, get rid of sugar and fructose. Then eventually your insulin level will return to normal, I guess. I didn't listen to the whole program. They were busy indicting the food industry when I turned it off, I had things to do. More sugar means more sales. You eat more, so more profit.