> (...) if you're not eating cake and stuff.

Ding ding ding. That's the nutrition part. I could easily eat that 700 extra calories by eating pizzas. Hell, I'd probably eat 900 extra calories after a big exercise. (But I would absolutely not run 30 km...)

The problem is that the people eating this stuff are continually being told that they need to exercise more. Then they get hungrier and eat the stuff that you can always eat more. They kill themselves on the treadmill and see absolutely no difference.