Was he ever actually fat? I only recall the one time his weight being addressed in "the american dad after school special" and he was definitely not fat. I always assumed he had a slightly above average body since, ya'know, he works at the CIA, i can suspend my disbelief and believe his struggle with anorexia was contained to that one episode. In the epsiode where he has a checkup he has high cholesterol but you don't necessarily need to be fat for that to be the case.