Sandi Toksvig has admitted it was her dramatic weight loss that gave her the confidence to move from radio to television.
Sandi, who lost four stone following Louise Parker's eating programme to drop from a size 22, said she might have stayed on the radio if she hadn't shed the pounds.
She told Good Housekeeping: "Maybe I would have stayed on the radio. I wasn't as comfortable. I didn't feel well. I had lost some confidence.
"At my worst I was a size 22, and at that size you can't go down the high street and buy yourself things that make you feel good. Your shopping options are limited in a way they aren't when you are a size 12.
"I'm not quite as thin as I was, but I certainly haven't put it back on again. Like most women, my weight goes up and down.
"The wonderful thing is I now have the tools to deal with it. Mostly now I don't eat carbs - actually I'm not attracted to them any more.
"There's no question that I'm fitter and healthier because I eat more fruit and vegetable. Turns out all the boring stuff you are told is true."
Sandi will be the first woman to host a major comedy panel show when she takes the reins from Stephen Fry to front BBC Two's hit programme QI.
While the presenter says she is excited to take on the role, she is disappointed it is still remarkable for a woman to host such a show.
She told the magazine: "I'm thrilled and it's an honour. And if it means that we no longer needed to talk about it, that would be even more wonderful.
"I was saying to Debbie [her wife] just recently that I'm only sorry I wasn't born 25 years later - that I didn't have to bang the drum for all sorts of things, that it just happened as a matter of course.
"But we are celebrating the fact we have a woman running for US president and, as far as I know, ruling a country isn't done with your genitals. It's insane that it has taken so long."
Sandi also dismissed claims she was "the female Stephen Fry", saying: "Well, I think it's more that he's the male Sandi Toksvig! You have to be yourself.
"You can't spend your time worrying about the shadows of previous people, however brilliant they were.
"You just have to decide that the show is going to be yours and that you are going to do it your way. I certainly wouldn't want to be a Mini-Me of any of the people whose footsteps I've followed in."
On working on QI, she added: "Honestly, this is the most fun I've had at work in 35 years. I've loved it. I was a little nervous but I know the show so well... Within five minutes I felt like I'd come home."
The full interview is in Good Housekeeping, on sale now.