Britney Spears one-time onscreen boyfriend Anson Mount is set to shock fans as a skinny meth addict in a new movie.

The Crossroads actor lost 20 pounds for the role in Cook County and admits his hunger started to affect his attitude onset.

He tells, "The schedule was grueling, shooting six days a week... and it was difficult being around me at times because I was pretty much consistently in ketosis. My temper would get a little short, so there were times I had to step away."

However, Mount insists he didn't simply lose the weight for the part - he took care to do it as healthily as possible: "I had to lose the body fat but I didn't want to emaciate myself to the point where I was losing muscle mass because that's actually quite dangerous. I think Christian Bale got to that point when he did The Machinist but I would never go that far. I don't think it was worth it.

"I consulted a personal trainer friend of mine who turned me on to a weight loss formula that body builders use... so I did that program and it turned out I started too early. I was ready two or three weeks before we started and I had to maintain it throughout the shoot, so it was difficult."

Mount's strict diet was also made more difficult as he was studying in France at the time.

He adds, "I don't recommend trying to lose weight there. It sucks not being able to have any wine, cheese, bread or chocolate."