Regarding those Biggest Losers who do manage to keep off their weight (and according to the former contestants I've interviewed that's a very small number) I've always said that the Losers who keep it off may well do so consequent to having translated their weight losses into careers as product spokespeople, celebrity trainers and motivational speakers.
Well maybe even that's not enough to help maintain the severity of a Biggest Loser lifestyle as one such Loser, Tara Costa, is apparently being sued because she'd gained back enough weight (according to news reports she had regained 29% of her Biggest Loser losses) that one of the companies for who she was a paid spokesperson felt that they could no longer use her in their advertising and that her weight gain in turn was in breach of her contract which specified that she needed to, "maintain her current level of fitness and conditioning".