"'Vell, young twenty stun,' said Sam, 'you're a nice specimen of
a prize boy, you are!'
'Thank'ee,' said the fat boy."

Perhaps some members are unfamiliar with UK measure of body weight, the stone = 14 pounds avoirdupois. So Sam weighs two hundred and eighty pounds. Definitely obese. Grossly so.

No, if I remember rightly Sam was quite slender, not to say skinny. He may have been exaggerating about the fat boy's weight. I don't suppose he actually weighed him.

Bingley