Lololol! Even tho I have a skinny face I am no near that thin, if you had looked under my shirt you would see that I actually have some mantits and floppppppy-wings on side of stomach
Jokes aside, what I mean is that ofc 10-20 KG over or under is not a biggie, but when a kid has like 50kg too much it's something wrong. The parrents need to take down their foot and tell force the kid to get healthier. Sure he will hate them, but in the long run he will be thankfull for the health benefits it gives him.