Robert Downey Jr. got in shape because he got sick.

The 44-year-old actor has had to get fit for his action-packed roles in "Iron Man 2" and "Sherlock Holmes," and although he has been exercising regularly an illness he picked up in Japan kick-started his weight loss.

“I was in Japan promoting ‘Iron Man’, and I went to a restaurant where I contracted a parasite and got really sick for three days.

"I started losing weight and thought to myself, 'Hey this is a nice jump-start!' It just gave me a nice little head-start with the first five pounds and then I kept going until I was thin, I felt as though I may float away."

Downey insists it’s important for him to be in prime condition for the roles because he has been asking the directors of both movies – Guy Ritchie on "Sherlock Holmes" and Jon Favreau who is helming "Iron Man 2" – to increase his stunt duties.

"The action's certainly got bigger on ‘Iron Man 2’ that’s because I went to do 'Sherlock Holmes,' which was a real adventure.

"So coming back to ‘Iron Man 2’ I really challenged our stunt team to get our hands a little more dirty because I was still kind of into that… I love it so much.

"There is no better day that I can have than one where I beat people up or get thrown around. I just love it.”