(Cover) - EN Showbiz - Justin Timberlake tries to "ignore the catering" when he is working on a movie.

The singer-and-actor strives to keep in shape and has a disciplined exercise and diet regime. Justin admits that spending long hours on movie sets can make it difficult to resist eating junk food in between takes.

"You have to ignore the catering. It seems like a pain, but it's really not that hard to monitor your own calories once you get it down. Plus, sometimes I can up my intake because I'm working 12-hour days and burning a lot more energy, especially on a movie like In Time, where it was so physical," he told UK magazine GQ. "All that diet and health stuff really revolves around the movie or show. I'm sure that there will be a project where I need to look unhealthy; I'll have to figure that out when the time comes."

Justin has appeared in movies including The Social Network, Bad Teacher and In Time. Filming can take months to complete, so he must ensure he doesn't lose or gain too much weight during this time.

"Sometimes I wake up and stretch and do 20 minutes on the treadmill, or anything to just break a sweat. And then I have the weekends where I can get out and play nine holes and maybe go to the gym. So I try and moderate it. It's kind of like running a marathon. The hardest part about making movies is staying the exact same weight every day and looking the same," he said. (C) Cover Media