In a few short months, actor Matthew McConaughey has shocked the public with dramatic weight loss for a new role.

After playing a muscular male stripper in Magic Mike earlier this year, the actor shed 38 pounds (17.2kg) of muscle mass to play AIDS patient Ron Woodroff in upcoming film The Dallas Buyers Club.

Speaking to HitFlix, the 43-year-old said: "I feel good, now. Overall, [I have] probably got 35 percent less energy. The tough part, there have been plateaus."

Speaking about the process of dieting and losing his signature muscle, he explained: "Getting past 170 was really hard, but then once you get into the 167, the next seven come off easy. Getting past 160, really hard. But then you fly down to 150. Getting past 150 was really hard. And then, bam, got down to 143 and that's where I want to be."

"Once you get past the plateau, the body seems to understand, 'OK this is where we're living now, this is where we are', so the energy rises," he added.

The star is currently in the midst of a five-week shooting schedule for the picture, but insists he won't return immediately to how he ate before the role, allowing himself time to adjust.

"The organs shrink, so my stomach has shrunk as well," he explained, "so as much as I can't wait to have that cheeseburger, on the day, it'll be damn hard to eat the whole thing."

The Dallas Buyers Club is expected to be released next year.