Nicole Scherzinger was "always very critical" of her body when she was younger.
The 39-year-old singer has admitted she is "more accepting" of her appearance as she has matured, but when she was a teenager she would go for long runs in the evening because she felt insecure about her body shape and wanted to be "thinner".
Speaking to Cosmopolitan magazine, the brunette beauty said: "I'm more accepting of my body now. I was always very critical of myself from a young age, and when I was 14, I started running. I would go outside in the middle of the night and run, because I thought I had to be thinner and that my thighs should look a certain way."
And The Pussycat Dolls band member has revealed when she entered into the girl group, which was also comprised of Kimberly Wyatt, Ashley Roberts, Carmit Bachar, Jessica Sutta and Melody Thornton, her insecurities "amplified" because she constantly had to flaunt her body in skimpy costumes.
She explained: "When I got The Pussycat Dolls, it really amplified that because it had so much to do with showing your body off."
However, the 'Buttons' hitmaker has learned to "embrace and accept" her appearance and not to be "so hard" on herself because it was "very imprisoning" for her.
She said: "But you should embrace and accept yourself more. Don't be so hard on yourself, and love your curves.
"It was very imprisoning and it stole all of my happiness, confidence and memories.
"A big part of that was during The Pussycat Dolls. I have a lot of fans and I never wanted to come out about it, because I was ashamed. But once I finally did come out about it, I realised how many people it had helped.
"Every woman has good and bad days."
Although Nicole has admitted she will have cheat days and will indulge in sweet treats, she relies on an intense work out session to stay "focused and positive".
The 'Moana' actress added: "Mrs O [Sharon Osborne] and I were joking the other day that sometimes we wake up in a puddle of cookies and crisps! But what really helps me is working out. Even if it's not for very long, [I love] to get a sweat on to keep me focused and positive."