Actor Jared Leto has rubbished reports that he gained weight for his latest film role by eating fast food.

The handsome actor packed on 20 kilograms (45 pounds) to play John Lennon's killer Mark David Chapman in the upcoming movie CHAPTER 27.

Media reports suggested Leto had resorted to eating hamburgers to help him bulk up for the role.

But he explains, "I did not gain weight for this role by casually eating burgers and fries.

"Besides the fact that I am a vegetarian and do not eat red meat, it's more important to state that I take this seriously and know the health risks involved."

The actor declined to explain how exactly he has gained the weight for his role.