Eminem replaced his drug addiction with something totally unexpected.

Eminem's long battle with drug addiction is intertwined with his music – he even documented his journey with two albums; Relapse (2009) and Recovery (2010).

But now the controversial rapper has spoken about how running 27 kilometres every day proved essential to his recovery.

In an interview with Men's Journal, Eminem (real name Marshall Mathers) spoke about how he discovered running after getting out of rehab following a drug overdose in 2007.

"When I got out of rehab I needed to lose weight [he weighed around 104kg during his addiction], 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," he said.

According to the 48-year-old, it was great at first – giving him a natural endorphin high and also helping him sleep. But his addictive nature soon took over.

"It's easy to understand how people replace addiction with exercise. One addiction for another but one that's good for them," he says.

"I got an addict's brain and when it came to running, I think I got a little carried away. I became a f**king hamster."

Mathers would run 27km a day on a treadmill – 13.5km in the morning before going to the studio and another 13.5km when he came home.

While he ended up losing over 40 kilograms, it started to do more harm than good as the rapper "started getting OCD" about the amount of calories he "had" to burn.

"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."

He then discovered at-home workout DVDs and started alternating between Shaun T's Insanity workout and running until it became too much and he gave up running altogether.

"I know a lot of these DVD guys are wacky, but I'm alone in my gym; I need someone on the TV yelling to motivate me," he told Men's Journal.

Now, the rapper says he has found one that suits his needs - doing the Body Beast workout every morning before going to the studio.

"The routine is pretty intense - the first time I did the legs, I couldn't walk for two days. Now I'm doing arms one day, chest the next day, legs the next, and I'm still functioning throughout the day," he says.

But that addictive feeling is still there.

"I'm pretty compulsive working out. I feel like if I step away from it for too long if I have a crazy week and take a five-day break, it'll be like starting over. I'm afraid that if it goes beyond that, I might lose the motivation," he says.

"Once you're at a place where you've made progress and you've got some time invested in it, you don't wanna quit and give up what you started."

Mathers has been open about how bad his addiction was, speaking about the experience in the documentary, How to Make Money Selling Drugs in 2013.

In an interview with Rolling Stone, he revealed that during the peak of his addiction; he was taking up to 60 Valium and 30 Vicodin pills a day.

After his 2007 overdose, doctors told him he was about two hours from dying.

Feature Image: Getty.