The TV presenter has told Bella magazine how she is worried her "poor body might not be able to cope much longer", as she vowed to "take some weight off her joints."
In an interview with the magazine, she said: "I know how much I weigh, but I'm so embarrassed by it I can’t say. I'm 20-something stone.
"It's the one thing in my life that I feel like I can't achieve. When you get really big like me, you don’t see any light at the end of the tunnel."
However, Alison has decided to start by making some small lifestyle changes, in the hope of losing a few stone.
"It's a slow process. It's all about eating clean and loving myself to the point where I want to look after my body."
The star previously had a gastric band fitted to help her lose weight, after being inspired by former 'This Morning' colleague Fern Britton's success with one, but her body rejected it.
She told the Daily Mail in 2014: "I was offered a gastric band around the time Fern was and tried it because Ii wanted to lose weight. I didn't have a trigger to say I was full up, which is why I had it. But my body started rejecting it. I began to grow scar tissue around it."
Of having it removed, she added: "The doctor said, 'Normally it takes 15 minutes to remove a gastric band but yours took three hours because of all the scar tissue."
Read the full interview with Alison in this week's Bella magazine, out now.
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