Splash! star Linda Barker said she was "astounded" by the reaction to her appearance on the diving show and admitted she had to be talked into wearing a bikini for the cameras.
The interior designer-turned television presenter said she credits her intense exercise regime for her slim figure.
She told Hello! magazine: "Exercise makes me feel good and confident, which is hugely powerful."
The star, who has just been signed up to front a lingerie campaign, works out twice a week with a personal trainer, runs marathons and practises yoga.
She said she did not expect the public attention she got after appearing on the ITV show.
She said: "After the first live show, my neighbour texted me to look online at all the comments like, 'how does a 51-year-old woman get abs like that?'.
"My husband Chris and I were having a cup of tea in bed and were just astounded."
Linda originally did not plan to wear a bikini, opting instead for a black running top and bikini bottoms - until a member of the wardrobe department intervened.
She said: "She came over and said 'you've got to wear a bikini'. I went, 'Really? Do you think I'll be all right?' "And she said, 'I think it will be fabulous. There'll be hair and make-up and glitter everywhere.' So I thought, let's do it."
Read the full interview in Hello! magazine on sale now.