scott: in the fall of 2009, danny cahill won season 8 of abc's reality tv show "the biggest loser" afterhredding an astonishing 239 pounds in seven months. but as the years passed, 100 pounds crept back despite his efforts to keep it off. >> i was exercising three or four times as much as the normal person and as that stopped the weight creeped back she lost nearly 75 pounds but has since regained 32 of them. >> i didn't people know i was on "the biggest loser" because i don't look like that anymore. scott: they followed contestants from the show. they found all but one of them gained much of the weight back. while scientists point out further research is needed, they concluded the contestants' own body were to blame. according to the study, they had normal metabolisms for their size before the show but after the show they continued to slow down, the mechanism for them to return to the original weight, further compounding the problem, researchers found the a p had plummets levels of hormone that leaves them hungry. >> it is metabolic adaptation. >> and producers of "the biggest loser" tr

all off their shoulders. >> over to robin. >> joining us "the biggest loser" season eight winner danny cahillr dr. jennifer ashton. thank you both. danny, so good to meet you. we heard in linsey's piece after you won and you said that you got your life back and you felt like a million bucks. what happened after that? >> you know, i did feel like a million bucks. after that, for a couple of years i kept the weight off completely. but i was -- i wondered why others were gaining it back but what i didn't realize i was working out two hours a day riding my bike all over town to go where i was going. i was exercising three or four times as much as the normal person and once that stopped, the weight started creeping back on. >> and so, when you hear this study, how do you process that information? >> well, number one, it's great because a lot of the shame that is on our shoulders, i mean, when you gain weight back even when you're in school it's shameful. when you're in front of america, then it's even -- it's ten times as shameful and so many people that i've talked to, including myself, when we f

>> you know, danny cahill lost 239 pounds, and he gained back 100. you know why?'re losing weight, stuart, is by a lot of exercise, which i approve of, but a tremendous restriction of calories which i think is a big stress on the system, and nobody can live with that 800-calorie-a-day business. so as soon as the spotlight is off you, you start eating anything. stuart: wait, wait, wait -- >> bang, 100 pounds come back. stuart: is it just a lack of discipline? you can't keep the weight off because you can't stop eating calories, or is it something to do with your metabolism? >> it's both. a, you can't keep that up, because of the lack of discipline, b, your body is going to rebel and not live in that starvation mode. i have to tell you, this may be good for tv ratings, it is not healthy to lose that much in seven months. if you have an underlying risk of heart disease or stroke, any of that, those ratings are going to drop tremendously if anyone ever has a heart attack -- it's not healthy. stuart: are you saying that you lose a lot of weight, you're going to regain