Glasgow, she says, made her famous - and fat.
"I came to the city to make it big," she says, adding with a snort of laughter: "Well, I was VERY big. Sixteen stone at one point..."
Diet is one of the subjects that multi-talented performer Karen discusses in a new BBC film, I Belong to Glasgow.
The four-part series, which starts on June 27, will also feature Alex Norton, Elaine C. Smith and Sanjeev Kohli.
Karen also tackles football - which she cheerfully admits she knows nothing about - leads a singsong in Central Station, and explores the city's lesbian and gay culture.
But while it is all very lighthearted, Karen admits watching the film for the first time was an unexpectedly emotional experience.
"I was surprised by how moved I was," she says, slowly.
"My dad died in April, and talking about my childhood - well, it made me feel emotional and glad at the same time, which sounds like a strange mix.
"My dad watched all my shows, he was always there."
There is a moment in the film when Karen reveals a message she wrote in her diary when she was 10.
"I, Karen Dunbar, swear one day to be on TV...world look out, here I come...I will 'forfill' this..." it says.
She smiles: "I always wanted to be on telly. One of my earliest memories was age four, belting out Que Sera Sera on stage in the Labour Club. My dad took me and he was watching me and clapping.
"It's a very evocative, powerful memory..."
Karen grew up in Ayrshire but loved visiting Glasgow, "the golden city over the hill."
She admits she moved away as a teenager partly to escape prejudice and homophobia.
"Once they took my cat, drowned it and left it in my garden with a note saying "you ****ing lesbian," she recalls. "I don't think I really ever got over that."
She adds: "Glasgow was a place of safety for me - there were pubs to go to, where you could spend time without fear of homophobia.
"The city accepted me for who I was."
Inspired by Elaine C Smith - "she was the first funny, Scottish woman I ever saw on TV and she made it seem possible" - Karen started singing in karaoke bars before she landed her first stage role in The Celtic Story in 1998.
Talking about it on film was another bittersweet moment as actor, writer and director David MacLennan, who died this month, cast Karen in the role.
"He took a chance on me because I'd never done it before - I was a pub chanter, standing beside Jimmy Logan and Dorothy Paul," says Karen. "It was a phenomenal experience for me. I feel gratitude for all the opportunities I've had."
For the film, Karen also joined a Radio Clyde football phone-in - "I know nothing about football, so it's a bit like being a vegan at a square sausage party" - and dressed up as a wee Glasgow wifey to visit a bingo club.
"Hardly anyone rumbled me - I had a riot," she beams.
She also visited Love Milton in the north of city, a community project supported by the Evening Times Streets Ahead campaign, which helps locals grow their own food.
"That was one of the highlights of the film for me," she grins. "I love talking to people, and I think I'm good at connecting with them.
"Spending time in Milton, getting a chance to understand their vision and see the kind of work they're doing, was a real privilege."
Karen is currently in Belfast, appearing in Can't Forget About You at the Lyric Theatre, directed by Game of Thrones actor Conleth Hill.
She won't be appearing in the King's panto this year, after the theatre announced both she and co-star Des Clarke had been dropped.
"You'd really have to ask them why," she says, politely, unwilling to discuss the subject any further.
"It gives me some space to do other things this year."
And she has exciting news about a forthcoming project... which she won't talk about.
"I'd love to tell you, I really, really would," she grimaces. "But I just can't ..."
So, as far as the diary note written all those years ago is concerned, Karen reckons she can look her 10-year-old self in the eye.
"I remember the last day of filming on The Karen Dunbar show - my very own telly show - and it felt amazing," she smiles.
"I thought if this is as good as it gets, then I've done it. And then it got even better.
"I feel like I have lots more to achieve but yes, I think I've 'forfilled' that little oath I wrote in my diary that day...."
l I Belong To Glasgow, BBC1, Friday, 10.35pm