'Biggest Loser' Castoff -- Contestants on Strike Are Sabotaging Their Lives

The oldest person ever to compete on "Biggest Loser" has some wise words for the contestants currently on strike -- the weight loss show is NOT about the prize money ... it's about saving your life.

TMZ broke the story ... nearly all of the remaining contestants on the current season have walked off the show and are threatening to quit -- after learning that producers were considering bringing back previous contestants to compete for the $250,000 grand prize.

The contestants are striking because they feel it's unfair to bring back old contestants -- which would hurt their chances at winning the money.

But 66-year-old John Forger (above) -- who competed on Season 12 -- tells TMZ, "It's not about [money]. What it's really about, for most of us, is the change in our lifestyle, and being able to get rid of obesity."

John adds, "For most of us, it's about health. Would I walk off the show for the money? ABSOLUTELY NOT."

John was eliminated in the second week of Season 12 -- but he tells us, he has no regrets ... losing 97 pounds while he was on the show, and an additional 15 afterwards.