The Take That singer - who has previously spoken about his battle with eating disorder bulimia - turned to food for comfort following the band's split in 1996 and didn't want to look at himself after reaching 17-and-a-half stone.
Barlow, 51, confessed in his one-man theatre show A Different Stage: "Now, a guy doesn’t want to see himself go through this.
"One morning I caught myself in the mirror and I thought, 'Oh no, I’ve got to do something about this'. So I did, I took down all the mirrors - massive house not one single mirror."
The Patience singer admitted he was so jealous of former bandmate Robbie Williams' solo success that his solution was to hide away, smoking cannabis and binge eating chocolate and junk food.
He said: "I got to 17-and-half stone, but it’s not all the work of chocolate, the real heavy lifting here is being done a few times a week down the road at the local Chinese all-you-can-eat buffet.
"They soon regretted that offer, believe me, because the all that I could eat was 10 fistfuls of prawn crackers, wonton, seaweed, spring rolls, prawn toast, whole crispy duck, sizzling beef Cantonese style, sweet and sour king prawn, ice cream and banana fritter, Irish coffee, After Eight mints and a Jack Daniels and Coke."
Barlow has previously spoken about that self-destructive period in his life.
Appearing on Lorraine in 2018 he said: “I was trying to kill off the popstar, that’s what I was doing I was eating away what a popstar looked like. I was just killing him off. Stopped dying the hair, stopped buying nice clothes, just wanted to look the opposite, physically and mentally.
"2003 – it was the day when I just went, 'No, I’m not having this anymore, I’m going to change. I want to change and I’m determined that this is not who I’ve become’."
Barlow revealed in 2021 he believes Take That – currently a trio – will reunite once more, this time with all five members performing together once again.
The Relight My Fire singers – Barlow, Williams Howard Donald, Mark Owen and Jason Orange – first formed as a boyband in 1990.
They enjoyed a hugely successful reunion in 2005.
Watch: Gary Barlow admitted he was jealous of Robbie Williams