The 'X Factor' judge, who has spent time in rehab getting treatment for her eating disorder and self harming, said she felt she was overweight from a very young age, and the insecurities have stayed with her.
"I remember being three years old in a diaper and rubbing my hand over my stomach... And I remember thinking in my head, 'I wonder if one day this will ever be flat?'," she said.
The 20-year-old, who has recently been named as the new ambassador of a bullying campaign, was targeted at school as the girls used to tease her for her appearance.