Matt Willis got "utterly addicted" to exercise.
The Busted bassist - who checked into rehab in 2005 to receive help for alcoholism - turned to working out to help cope with his issues with drink and drugs but eventually became obsessive and would get "angry or upset" if he didn't have the time to hit the gym.
Speaking to Fearne Cotton on her 'Happy Place' podcast, Matt said: "Exercise was a big thing for me... when I found it I was completely and utterly addicted to it.'
"It was great because everything about it was positive.
"And then it became a problem where if I didn't or something got in the way of it I was triggered or I became angry or upset."
Matt - who has Isabelle, 12, Ace, nine, and Trixie, five, with Emma - recently admitted that the COVID-19 pandemic left him fearing for his career.
The 39-year-old musician confessed that lockdown restrictions and the closure of live events left him in fear for the future, as "90 percent of [his] work is in front of a crowd".
He said: "I’d been renting a music studio in Watford for the last few years, that was the place where I would go and write songs and be creative. When Busted took a break I went back to drama school, and when the first lockdown happened suddenly that was taken away as well.
"Then everything I had lined up was either postponed or fell through, or postponed and then cancelled. Everything felt out of reach.
"I found it really tough at times to figure out what I should be doing. What happens if I can’t do these things? 90 percent of my work is in front of a crowd so I was starting to worry."