The Superbad actor told Metro that while he has improved his diet in recent years, he has not stopped drinking.
"I try not to eat bad stuff anymore but I can't give up beer, that's the one thing," Hill said. "I wish I could but I can't."
Of whether he lost weight to boost his career, he added: "I think there have been a lot of really talented dramatic actors who are all different shapes and sizes.
"I was big in Moneyball and that's been the most praise I've ever had. I think getting in better shape is a sign of maturity, of taking things more seriously. And I'm evolving as a person, as well as an actor. Plus, I feel so much better."
Hill said: "I went to see a movie recently and they had a trailer for The Sitter followed by one for my next film, 21 Jump Street. I looked so different in the two."
> Jonah Hill: 'SAG, Golden Globe nominations are thrilling and surreal'
Watch a trailer for The Sitter below: