Naps, I too have no issue putting on muscle mass (without going to Chubby's link,lol!!!) but not all people are built the same (mesomorph). My workout buddy ate six lean meals a day, had the vitamins, all the protein shakes and busted his nuts in the gym and would be lucky to put on a pound a month. It's called being an ectomorph a typically lean muscle mass, whereas some of us who are mesomorph's have little problems gaining muscle mass.
He actually broke his knee cap in a fall 15 years ago and his leg atrophied over his recovery and no matter how much he trained it after it's never equalled out!
P.White clearly looks to have an ecomorph body type and would have a tough time putting on alot of weight in a short time.