And De Laurentiis is largely the reason Higuain is turning out for Juventus - they clearly don't get along and that goes beyond Higuain's body fat %. Incidentally he's pretty obviously in better shape there than he is in the image Bryant posted above.
Higuain looks no more out of shape than Rooney or Cazorla ever have. As I say, his weight is clearly not a significant detriment to his performances since he's just broken the record for most goals in a single Serie A season. And Juventus wouldn't make him the third most expensive transfer of all time either.
Maybe you're right and it's something he struggles with on a personal level despite the level of support he gets around him. In which case there's nothing you can do about it and you'd still be better off focusing on what he can do.