Singer Demi Lovato has opened up about her past struggles with alcohol, drugs and body image in a new revealing interview with US in-flight magazine American Way.

The Cool for the Summer performer – who first checked into rehab when she was just 18-years-old – told the mag she thought she’d be dead before ever reaching her 21st birthday.

The star said:  “I lived fast and I was going to die young.”

“I didn’t think I would make it to 21.”

Demi was admitted to rehab for three months in 2010 after she punched a back-up dancer while on tour with the Jonas Brothers.

Speaking of the experience she told American Way: “I thought, ‘Oh great, now the world thinks I’m just another stereotype.'”

“I thought, ‘I’m not in treatment for a drug and alcohol problem.'”

“But once I started eating again, the other issues got worse. It was like whack-a-mole.”

While attending the centre Demi – who has since fought her addictions to alcohol, cocaine and the prescription painkiller OxyContin – was diagnosed with bipolar disorder – a condition her late father also suffered with.

In the interview, Demi revealed that both her mother and grandmother had previously dealt with bulimia – the same eating disorder she eventually went on to develop.

She said: “Being around somebody who was 80 pounds and had an active eating disorder…it’s hard not to grow up like that.”

“Hopefully my kids won’t have it, but it’s kind of like addiction…It’s hereditary.”

She also admitted that her issues with body image were enhanced by taking part in beauty pageants as a child where she “judged for her beauty”.

The 23-year-old celebrated her fourth year of sobriety back in March but continues to receive support at regular Alcoholic Anonymous meetings.

Demi also explained to the mag how being honest about her issues has benefited both she and her fans.

She said: “When I have meet-and-greets, I can’t tell you the amount of times that girls will show me their arms covered in scars or cuts.”

“They’ll tell me, ‘You helped me get through this. Because of you, I stopped self-harming,’ or ‘I got sober.’ Hearing those things gave my life new meaning.”

“At times I was resentful for having that kind of responsibility.”

“But now, it’s really become a part of my life. It holds me accountable.”

Feat image: BBC