Coll said that having gastric by-pass surgery, although a very serious and tough operation, has "turned [her] life around."
She used to wear size 22 clothes and is now a size 10, plus she has recovered from the numerous health problems that were plaguing her.
"I've struggled with my weight for 15 years and I've tried everything and this is a final last resort," she said.
"I would consider myself to know a lot about nutrition and I was either on the healthy bandwagon or off it...I was Yo-Yoing all the time. I could never get control of it.
"So now my life? completely different."
Watch the full interview above.
Nine Stone Lighter is on RTÉ Two on Thursday October 1 at 9.30pm.