Yes, I think that the weight lost on the Biggest Loser is sustainable, because the people on the show are also given education about lifestyle. They are taught about nutrition. They are taught what to eat and not eat. They are taught how to keep up an exercise program and stay motivated.
Yes, weight loss achieved on "The Biggest Loser" can be sustained if contestants find a way to take what they learned on the show and apply it to their normal life. However, it will take hard work and dedication to continue to lead a healthy lifestyle after the cameras have stopped rolling.
I do not think the weight people lost on "The Biggest Loser" show is sustainable. I believe most of them will be back up to their original weights within two years at the most. The show provided the contestants with a goal, constant motivation, and work out regimens. They were given all the tools necessary to successfully lose weight. Once they leave the show, they will have to motivate and manage themselves without a professional helping them.
I have my doubts weight loss on The Biggest Loser is sustainable. The period the show is created in is far too short and the changes made to the peoples routine are more than likely not sustainable without a personal trainer. It takes a long time to change food and exercise habits and I do not think the show supports that aspect.