The Weatherfield actress, who plays Eva Price, lost five stone a decade ago after being told by a producer that she could only play a larger role.
Tyldesley recalled: "I went for an audition to play Rizzo in Grease and the producer said to me, 'Sorry, Cath, but you will always be the fat character actress', and I didn't get the role.
"After that, I thought, right, I want to be a professional actress and I need to get healthy. I lost the bulk of it in a year," she added.
Tyldesley, 29, has been nominated for 'Sexiest Female' gongs twice this year in the British Soap Awards and the Inside Soap Awards.
Speaking in the summer, the star claimed that she never gets approached by men.
> Coronation Street Catherine Tyldesley: 'I'm like Mr Bean with boobs' Get the Inside Soap magazine on your iPhone or iPad