But the 56-year-old Loose Women presenter – who has openly struggled with her weight for many years and admits trying "every diet going" – insisted it was an unexpected side effect of a new plant-based diet she took up for health reasons.
Coleen said: "I never weighed myself. The weight comes off. What I'm bothered about is I feel so much better. Best I've felt for years.
Read more: Linda Nolan admits she's 'scared of dying'
"The main reason for doing it is my sisters' cancer diagnosis and family members have diabetes. I've got to do this now."
Last May Coleen's older sister Anne, 70, was diagnosed with breast cancer, on the same day their sister Linda Nolan, 62, was told her cancer had returned. Another sister, Bernie, died aged 52 in 2013 after battling breast cancer.
Coleen admitted she hadn't enjoyed her vegan diet at first, but has got used to it.
She said: "Here's the thing – some of it I don't like. I love my dairy and chocolate, but I've really got used to it and trained my taste buds.
"I'm eating to live rather than living to eat."
Coleen previously revealed she was told by a TV boss that she was "too big" to present primetime TV.
Watch: Jenny Eclair discusses her sacking from ITV's Loose Women
She revealed at online event A Girls Night In With Melanie Blake: "I have had a head of a big TV company saying: ‘If you want to get in primetime television you should get a gastric band, you’re too big to present primetime.'
"I’ve had, 'Oh, you’re getting on a bit now, so maybe you’re not right for primetime.'
"And yet you see all these guys in primetime, some overweight, some certainly in their 60s and 70s. There don’t seem to be any women of a certain age or a certain size in primetime."
Watch: Coleen Nolan claims she was invited to a hotel room by Jimmy Savile when she was 14