The Poison rocker also revealed he did 2,000 sit-ups before he took his clothes off for Billboard magazine.
Bret, 47, shows off an impressive six-pack on the cover of the music trade publication.
He said: 'I didn't eat for a day and I did about 2,000 sit-ups.
'I said, 'Listen, I have two requests [for the shoot] - good lighting and a warm room. That's all I'm asking for'.'
He added: 'If I'm walking out with it all ****ing hanging out there for the world to see then, well, I need good lighting and a warm room.'
The singer almost died earlier this year after suffering a near-fatal brain haemorrhage.
He appears on the cover of Billboard's 'Maximum Exposure' issue, which is on sale now.