The ex-Liberty X singer, who has lost two stone in the last year, claimed that she was inspired to shed the weight by snaps of her on a night out in Dublin.
"There was a picture of me outside a club in Dublin and I was wearing a pink Lipsy dress," she told New magazine. "I just remember thinking, 'Oh my God - I look hideous'. I was trying to kid myself and squeeze myself into a size 12 dress when really I was a size 14.
"I was smiling for all the photographers, but I was desperately unhappy underneath."
She continued: "People are often ashamed to wear certain dress sizes. I know I was. I would buy something in a small size and promise myself I'd get into it, but you never do. It will sit in the closet."
Heaton joked that the only drawback from her recent weight loss was her boyfriend Hugh Hanley's disappointment at her reduced breast size.
"Hugh said he'd like a little bit more weight, but in the bra department! It seems to come off the boob area first," she said.