Rumours had begun to spread that the picture was digitally altered to make the Aussie actor look buffer.
But Hugh insists his impressive physique was down to hard work and nothing else.
Appearing on The Jeff Probst Show, Jackman said: "That's all me, man."
The X-Men star said he was peeved at the suggestion it was a fake, saying: "Because it was brutal getting there. And by the way, I asked the company if they could just... you're spending millions on special effects, just help me out. I want to eat pizza and drink beer. And they said no."
He added: "For that kind of body, I had to go up in weight, big, lift big and heavy, then strip down."
Hugh recently revealed that The Wolverine - which is scheduled for release on 26 July 2013 - will feature a cameo by one of his former co-stars.
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