Jared Leto is ''terrible'' at eating a lot.

The singer-and-actor needs to bulk up to play the Joker in the forthcoming 'Suicide Squad' movie but the 43-year-old actor - who is vegan, meaning he doesn't consume animal products - is finding it hard to gain weight.

He said: ''I'm trying to gain a lot of weight. It means I have to eat every couple of hours -- and I'm terrible at eating a lot.''

The 'Dallas Buyers Club' star is excited about the ''challenge'' of portraying such a ''beautiful disaster''.

He told Billboard magazine: ''The opportunity to take on this nearly Shakespearean character -- that's what graphic novels and comic books are becoming, right?

''[He's] this beautiful disaster of a character -- what a big challenge.''

While Jared's diet is making it hard for him to gain weight, he has previously credited it for his youthful looks.

He said: ''It's probably just down to sleep and diet. If you travel long-haul a lot or don't sleep much, [your body's] not going to last very long, that's for sure.

''I'm pretty healthy so I think that helps a lot. I've been that way for a long time. Twenty solid years of eating vegetarian/vegan and taking care of myself. That probably helps the preservation process.''