It's a long story. His description of "dieting" was extreme calorie restriction. He was eating something like 800 calories per day (don't quote me on the exact number) and then was complaining that he didn't feel well when doing that (to the surprise of absolutely nobody).

Then it turned into a false dichotomy between the 800 calorie severe calorie restriction or no dieting at all. Then he just started declaring he'd delete any comments that suggested dieting.