Its not only a game of weight loss, but also one of strategy.
Take Survivor (eurgh, haven't watched it for years, but meh, my point still stands), it is often the "weaker" players that make it through, riding on the coattails of others, out "outwitting" the others to make it to the end.
As far as I see, there is nothing wrong with this. If you were to have a game that the final three were determined purely by who had lost the most weight, who would you have? Probably, my guess would be Wal, Harry and Shane, an all male group who may or may not deserve to win.
Yeah, fundamentally the game is about losing weight, but its not purely about how much you can sweat it out in the gym, but how well you can win by using your head.