Eminem's prescription drug addiction left a hole in his stomach.
The Real Slim Shady rapper saw his weight balloon to 230lbs at the height of his problems, and attributes the gain to trying to relieve stomach ache brought on by the discomfort caused by drugs such as Vicodin and Valium.
He said: "In 2007, I overdosed on pills, and I went into the hospital. I was close to 230 pounds. 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."
After leaving rehab, the 42-year-old star was determined to tackle his problems by exercising, but quickly found himself with a new addiction, to running.
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Writing in the September issue of Men's Journal magazine, he added: "When I got out of rehab, I needed to lose weight, but I also needed to figure out a way to function sober.
"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. I would get up in the morning, and before I went to the studio, I would run eight and a half miles in about an hour. Then I'd come home and run another eight and a half. I started getting OCD about the calories, making sure I burned 2,000 every day. In the end I got down to about 149 pounds.
"I ran to the point where I started to get injured. All the constant pounding from the running began to tear up my hip flexors."
- Bang! Showbiz