The 1.73 metre tall rapper blew up to weigh more than 100 kilograms after leaving rehab, he tells Men's Journal in the September issue.

"In 2007, I overdosed on pills, and I went into the hospital," says Eminem, whose real name is Marshall Mathers. "I was close to 230 pounds [104 kilograms]. I'm not sure how I got so big, but I have ideas. The coating on the Vicodin and the Valium I'd been taking for years leaves a hole in your stomach, so to avoid a stomachache, I was constantly eating — and eating badly."

The 42-year-old told Rolling Stone just how badly in 2011.

"I was going to McDonald's and Taco Bell every day," he told the magazine. "The kids behind the counter knew me – it wouldn't even faze them.

"Or I'd sit up at Denny's or Big Boy [hamburger fast food restaurants] and just eat by myself. It was sad. I got so heavy that people started to not recognise me.

"I remember being somewhere and overhearing these kids talking. One of them said, 'That's Eminem,' and the other said, 'No it's not, man – Eminem ain't fat.' I was like, 'Motherf---er.' That's when I knew I was getting heavy."

After leaving rehab, the SoundScan's Artist of the Decade, who has sold 32 million albums in the past 10 years, decided it was time to do something about it.

"I needed to lose weight, but I also needed to figure out a way to function sober," he tells Men's Journal.

"Unless I was blitzed out of my mind, I had trouble sleeping. So I started running. It gave me a natural endorphin high, but it also helped me sleep, so it was perfect. It's easy to understand how people replace addiction with exercise.

"One addiction for another but one that's good for them. I got an addict's brain, and when it came to running, I think I got a little carried away. I became a f---ing hamster. Seventeen miles a day on a treadmill."

He has since toned down the intensity of his exercise and no longer drinks, but if his daily diet is the same as in 2011 when he spoke with Rolling Stone, there's still room for improvement.

"I'll get up around 7:30 or 8:00 and work out," said Mathers who lost nearly 40 kilograms.

"I was working with a boxing trainer for a while, but now I just run, bike, hit the heavy bag. I eat breakfast – low-fat waffles with sugar-free syrup and a Red Bull – and then just get to the studio as early as I can, try to put in a full day's work so I can get home early enough to see the kids."

Mathers has three children. Daughter Hailie​ Scott, 19, who is Eminem's biological child with ex-wife Kim, Whitney Mathers, 13, who is Eminem's adopted daughter and Alaina Mathers, 22, Kim's twin sister's daughter who Eminem has also adopted.

Fairfax Media