The presenter posed at a typical US diner and revealed that she would rather have a curvaceous body than a life without junk food.
"I'm not a fitness buff," she claimed. "I like having curves. I will never diet. I love burgers and I love chips.
"I like good food and I'll eat until I'm full. I have a panic week in the gym two weeks before The X Factor starts, but that's about it."
Flack also talked about her complicated relationship with Xtra Factor co-host Olly Murs, likening him to a relative that it's okay to "have a little flirt" with.
"He's like my stepbrother. I say "step" because it means we can still have a little flirt on screen. Because if you flirted with your brother it would be weird. I don't think we fancy each other, we just flirt."
Asked to sum up her fellow X Factor judges, Flack described Gary Barlow as "a lot funnier than people think", Louis Walsh as "a gossip" and said that "mother hen" Tulisa Contostavlos "would always have your back".
Revealing that Nicole Scherzinger can do a "quite good" Essex accent, Flack continued: "I want to grab her hair sometimes and mess it up. She always looks perfect."
The full interview appears in this week's Heat, on sale now (October 9).
Watch Flack on The Xtra Factor, ITV2, Saturdays and Sundays, and check out her X Factor column, only in Heat.
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