relative to size that you don't realize how many calories you're consuming. The article below describes a professor from KSU who consumed only sugary foods, but limited his intake to 1800 calories. Despite a crappy diet, he lost a significant amount of weight, his bad cholesterol decreased and his good cholesterol increased.
I think I'd feel pretty crappy if I followed that diet, but it supports the theory that it's not what you eat, but rather how much you eat.