Jared Leto says gaining weight for film roles is harder than losing it.

The 42-year-old actor piled on the pounds for 2007's 'Chapter 27' - where he plays John Lennon's murderer, Mark David Chapman - and this had major health implications.

He explained: ''Gaining weight is far more difficult and damaging. It changes you so much, it's wild. For 'Chapter 27', I was drinking melted Häagen-Dazs, olive oil and soy sauce. Not fun. My cholesterol jumped up and they wanted to put me on Lipitor, a cholesterol drug for older people.''

Jared - who took a six-year break from Hollywood to work on his music career with band 30 Seconds To Mars - was forced to lose weight for his latest role as HIV positive transgender woman Rayon in 'Dallas Buyers Club'.

Although the Hollywood star understands appearance can add to one element of a character he thinks there are a number of other things which also need to be perfected in order to play a part well.

He told ShortList magazine: ''To play Rayon, I just ate nothing for weeks. But I think both of them [weight loss and weight gain] are less about how they make you look, and more about how they make you feel.

''In the case of 'Dallas Buyers Club', the weight loss provided a fragility for a character that's addicted to drugs and dying of Aids, but it's not like you lose the weight and then you're automatically able to deliver the performance. It's just one component in the whole process.''