The British-born star said that cruel comments about her weight 'broke her heart' and sent her spiralling into drug addiction.
The 26-year-old told told Shape magazine: 'It sets you up to hate yourself in a huge way. I was so angry about the things people said about me. I truly believe it's the main reason I turned to Vicodin and ended up in rehab three times. I just hated myself.'
Kelly, who rose to fame on TV reality show The Osbournes, said that she also turned to food for comfort when she was feeling down.
She added: 'I used to eat chips and cookies and drink soda all day long. I had to start making better choices.
'I indulge with pizza and cheese - I love Brie - and have cookies sometimes. But now, when I'm full I stop eating! It may have taken me 26 years to figure it out, but I've finally learned how to do it right.
'Diet and exercise really work!''