Surviving a crisis is one motivation for keeping fit, according to Ashton Kutcher.
Kutcher and his wife Demi Moore are committed to tackle the tough Master Cleanse diet once a year - to get their bodies prepared for a potential food shortage.
The actor fears the end of the world is close and the Hollywood couple is trying to be as fit as they can so that they could survive on as little as possible, reports Contactmusic.
So they have decided to live on nothing but water, maple syrup, cayenne pepper and lemon juice for 10 days once a year.
"If the s**t hits the fan, I like knowing I could live off water and syrup for a couple of weeks," the 'Killers' star tells Men's Fitness magazine.
Moore and Kutcher kicked off their first Master Cleanse earlier this year and tweeted about how tough it was.