I wouldn't say this friend is fat (not neccesary), but he is definetely overweight. It does not matter if this is pure muscle or just fat, he still weights a lot. And it will strain his joints, it will deform his posture etc. He could look bulky as fuck and bench press half a cow, but still is overweight.

Actually, most gym guys are overweight. They have heathly ammount of fat, but excessive muscle mass. It's obviously better than just being fat, but still they are less healthy in general than some skinny guy who just does some cardio. It applies to your friend too - he is now young and bulky, he plays demanding sport, but he is straining his health a lot by doing it.