He looks like he's been working out, maybe he's one o' those "bodybuilders" we've heard so much about.
They build mass and shape muscle by lifting weights or similar in a gym of sorts.
I also heard (from a reliable source), that you eat meat and potatoes, adding spinach every third week, your arms could grow like that.
Talked with a dietist and a dentist last week and they said something like this, if you want arms of epic proportions, the atkins-diet is not the way to go.
Rinse and repeat with flouride and the results will come very quickly, noticable results after three weeks or similar.
"Hope this helps."