Mine is a giant (born 7.5lbs, now 17lbs and 26" at 3mo), but babies need what they need - they don't get "overweight" in the adult sense. Nor do they need to be limited in how much they are given. Mine have all been different in how they grow - this guy is off the charts in weight and length, my daughter has always been on the 50%, and my eldest was off the charts on height but not weight so a skinny guy.
But I agree with above - 16lbs doesn't seem that massive! Especially given his length.