>>81871642His annoyingass dad shames him, that's the core of the problem.
As for the second question well there's a lot of things like ordering lots of fast food he likes and then eating very little yourself, extra oil in everything I cook for him, always leave him sweets and snacks everywhere, always ask him to finish my meal when we go out to eat, just cook him big portions in general etc. it's not hard cuz he likes to eat. Sometimes I'd make him something "healthy" like a fruit smoothie and then put a bunch of cream in it, he doesn't understand it.