We've all seen the pictures of matthew McConaughey. But he's speaking out for the first time about his dramatic weight lose. It's for his latest role. The star lost 40 pounds, becoming almost... See More
We've all seen the pictures of matthew McConaughey. But he's speaking out for the first time about his dramatic weight lose. It's for his latest role. The star lost 40 pounds, becoming almost unrecognizable. But he already has plans for how he will put the weight back on. And here's abc's bazi kanani. Reporter: Fwans can't believe that this shocking skeletal figure is the same matthew McCONAUGHEY, WHO A FEW MONTHS Ago, looked like this. I see a lot of lawbreakers up in this house. Reporter: But since this summer's "magic mike" the hollywood hunk has suddenly shrunk, intentionally dropping weight for his next role, as a man suffering from aids in the '80s. I feel good now. Overall, probably have 35% less energy. Reporter: It's a dramatic transformation for the former sexiest man alive. THE transformation McConaughey says has not been easy. I don't want to be doing this interview at a pizza hut buffet. I choose my places where there's less good smells. Reporter: The six-foot-tall actor has dropped from 181 pounds down to just 143. That's nearly one-fourth of his total body weight. It's 90% diet. It's 90% amount of what you're eating. Right now, I'm not losing anymore weight if I burn 1,500 calories, and 2 hours of cardio an afternoon. Or if I don't. Reporter: What does matter to health experts is that McCONAUGHEY'S EXTREME WEIGHT Loss could set a bad example for his fans. You're talking about someone losing their body weight in a six-month period could put them in jeopardy. Reporter: Mcconaughey says while he's eager to start beefing up as soon as possible, it may now be difficult. The stomach has shrunk, as well. As much as I can't wait to have that cheeseburger on the day, it will probably be damn hard to eat the whole thing. Yeah. Reporter: Fans of his earlier works are probably hoping he'll try. For "good morning america," bazi kanani, abc news, new york. I never had a problem eating a whole cheeseburger. Again and again. He is a laidback kind of guy.
This transcript has been automatically generated and may not be 100% accurate.