The X-Factor judge gave birth to son Ethan seven months ago and said that she wanted to make sure that she lost the weight slowly.
Speaking to Woman's Day magazine, the 39-year-old said: 'I have just about lost all of the pregnancy weight, but I haven't been exercising much. I haven't had the time or the energy. I've done one exercise session! But running around burns calories and so does the no-sleep thing.
'When I got pregnant, I started eating sweet things for the first time and I haven't stopped. I read this article that said I was on turkey broth and crazy exercising every day. I don't eat meat and I've been eating lemon pie.'