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Getty Images North America 1 / 7

Singer JoJo hit it big (really big) in 2004 with hits "Leave" and "Baby It's You" as an adorable 13-year-old. A few years later, she was under such pressure to lose weight to advance her career that she went to extreme lengths.

She actually took injections to lose weight, she told Popsugar.

"Here's something that I agreed to do that ended up messing with me psychologically," she said. "I was under a lot of pressure with a company I was at previously, and they wanted me to lose weight fast. So they got me with a nutritionist and had me … on all these supplements, and I was injecting myself — this is a common thing 'the girls' do, by the way — it makes your body only need certain calories, so I ate 500 calories a day. It was the most unhealthy thing I've ever done."

JoJo said she was about 17 or 18 years old when she took these injections, but didn't explain exactly what they were.

"I felt terrible about myself, and I was upset that I even subscribed to the standard they wanted me to be at," she said.

JoJo ended up gaining all the weight back.

She said, "I felt like, 'If I don't do this, my album won't come out.' Which it didn't! So it's not like it even worked!"

JoJo had been off the pop music radar for more than a decade before released a single last year and showed off her mature and gorgeous look on Instagram in August 2015. In her sexy Instagram post, she showed us just how much she'd grown up, donning a white one-piece swimsuit as the wind wisped through her hair.

"Oh ya know... Just surveying the in the city in my white bathing suit and silk kimono," she wrote, before plugging her new official website.

A far cry from that young teenage girl, JoJo said she doesn't feel the pressure like she once did.

"I listen to other people's opinions. Listening and following are different things," she told Popsugar. "I think listening and showing respect to people you respect … it works for me. What you think about yourself and the decisions you make is what's most important."