My 10 year old boy is 4ft9 and rather plump, he has chunky thighs, a fairly large belly and a fat face. But i've recently noticed how big his bum is, it's by far the fattest part of his body and looks slightly out of proportion compared to the rest of him. It seems unusual for a boy to have this issue. Anyone know what causes it ? Should I be concerned at all ? Any answers will be much appreciated :)