That is not a contradiction at all. Fat people are fat for a reason, though it is not intentional. They eat because they like food, not because they want to be fat. He has a good build because of his job, not because he wanted to look that way.
The only reason why he got to look that way is because he started working in middle school to support his brother and sister. Also for the fact that they are poor so they cant really afford large meals for him to gain any weight.
Tummy gap (when you lift your arms and your shirt comes up, or your shirt sticks to the inside of your jumper when you take it off) is like the chick/gay dude equivalent of accidental side-boob.