Fearne Cotton developed an eating disorder as a teenager after "feeling fat next to tiny, tiny pop stars".
The 38-year-old star became bulimic at the age of 19 after her dream role as a presenter led to her developing "that comparison disease".
Speaking on 'The Joe Wicks Podcast', she explained: "I was thrust into this weird world. I was a normal kid going to a state school in London and the next minute I was sat next to these tiny, tiny pop stars in a TV studio going, 'I don't look like that, I don't fit in here'.
"I was a teenager with puppy fat, like all teenagers have, and looked very regular and normal. But as perfectly fine as I was, I instantly had that comparison disease, where you sit and look at other people and think, 'Oh God, I don't fit in, this is awful'.
"I felt like that for a long time. I dipped into this world of bulimia from the age of 19. Looking back, I disregarded bulimia for a long time and didn't see it as a mental health illness, I just saw it as a weird thing for me to be doing.
"Now I really honour that it was me looking for coping mechanisms because I didn't feel mentally strong enough to deal with what I was dealing with in my career. I had moved out, I had been independent for a very long time at that point, I was juggling 'Top of the Pops Saturday' and 'Top of the Pops' - it was pretty relentless."
Fearne - who has Rex, seven, and Honey with her husband Jesse Wood and is stepmother to his children Arthur, 18, and Lola, 14, - also revealed that being in the public eye from the age of 15 made her an easy target for criticism.
She explained: "When you're in the public eye at 15 relentlessly, until you're the age I am now, you get a lot of people saying a lot of s***** things about you.
"A lot of people are naysayers, don't agree with what you're doing or just don't like you for no reason. You become a very easy target. I've had some really tough times."
Fearne previously opened up about how the "intense" eating disorder "ruled" her life during her 20s.
She said: "It's been this weird secret I've felt a little bit embarrassed of, a little bit ashamed of, a little bit worried about. I'm still worried now about what people are going to think when I share this side of myself. I had this new release I invented for myself - to have bulimia. I had that on/off for a good decade of my life."