Survival training was a required course for Earth Starfleet and MACO personnel in the mid-22nd century. The Starfleet course involved living on recycled sweat and snake meat for a prolonged period of time.
In the early 2140s, Malcolm Reed stopped eating food for a whole week, instead choosing to live on water and apple juice. His sister Madeline related this to Hoshi Sato in 2151, though she couldn't remember whether it was for survival training or a contest. (ENT: "Silent Enemy")