In an exclusive interview for the Mirror, she revealed that she had lost seven and a half stones - because "I want to be there for my kid" - by eating less and exercising more.
But she said she had put back on a stone because "I have more treats now!"
She said: "When you're over 50 you have to pay attention to your health a bit. I want to be there for my kid.
"I have quite a lot of exciting adventures that I want to do, and I had just ballooned a bit more than I wanted to. I've never disliked myself, and my weight has had nothing to do with my self-esteem. I still refuse to dislike my old body."
But Dawn said she was concerned about her daughter Billie, who she adopted with her ex, comedian Lenny Henry.
"She is a 20-year-old girl and like all 20-year-old girls that I've ever met she has all sorts of feelings about her body as I did when I was 20, but no more than any other kid," Dawn said.
"I listen to her and her friends all the time sitting round our kitchen table and they talk of little else than what they look like and stuff, which is a shame.
"Jen (her comedy partner Jennifer Saunders) and I were talking about this the other day - how funny it was that at that age we thought we were hideous monsters.
"But we look at pictures of ourselves now from back then and we weren't hideous monsters at all. It's not just that we're older now - we actually were lovely young girls just as they are lovely young women.
"You just don't know that when you're going through it, that's the shame. But it' s definitely worse for girls today - because size zero has happened.
I can't begin to understand that. Why would anyone want to be called a size zero or even aspire to being a zero?
"But then I've never been in the world of ordinary dress sizes - and I'm still not. I've always been on the edges of that, since I was tiny.
"Tiny in age, I mean. I've never been tiny tiny. It's just shocking and upsetting that my daughter and her friends feel pressure to be much thinner than they should be.
"Luckily Billie hasn't suffered from any eating disorders, but some of her chums have and it destroys families.
"For me, whatever age or size I've been, I have rather liked myself."
• Dawn was speaking to celebrate the mums of some of our biggest Olympic stars. You can watch their video here.