Contrary to popular belief, not all manboobs are caused by fat. Some men are naturally born with higher amounts of estrogen then others and once they hit puberty start growing actual breast tissue. In fact, almost 1/3 of evry male has some form of it, though it may not be noticable.
But yes, most manboobs are just fat on overweight people.
Joe: Have you seen Aaron'smanboobs lately? They're HUGE!
Bob: Yes, I have; They are indeed, LARGE.
By Reeva
Manboobs
Dangling mass of fat found on males that dont get out nearly enough. I emphasize the last part because they clearly need some exercise instead of sitting on their asses all day playing video games and watching tv.