The 37-year-old actor admits he is finding it tough to lose the excess pounds he gained to play a whistleblower in 2009 movie 'The Informant', but recently started learning to box in an effort to slim down.

He said: "If you put it on, it's easier to get it back off. I'm just boxing. I figure if you get hit enough times, it will fall off!"

Matt, who was named one of the Sexiest Man Alive in 2007, laughed: "Now I'm the Sexiest Man Alive's chunky cousin!"

Meanwhile, the 'Bourne Ultimatum' actor - who has a nine-year-old stepdaughter Alexia and two-year-old daughter Isabella with wife Luciana - revealed it was his children who inspired him to join forces with One X One Foundation, a charity which helps children worldwide.

He told an American newspaper: "It's about helping kids. It's not like before I was a father I was like, 'The hell with those kids.' But something does shift when you have a child of your own. It's hard not to look at every child as somehow connected to you."