dr. rob huizenga. >> i think it's a barbaric procedure. >> she's also a plastic surgeon. could never advise a procedure that would cause a patient pain. pain is not a good thing for anybody. >> reporter: better known as "dr. h," he specializes in long-term weight- loss, spending fourteen seasons as an expert on "the biggest loser." >> this is so primitive an approach. you could hire somebody to hold a gun to your head and threaten to shoot you every time you eat. you could have somebody with a hammer hit you over the head every time you threaten to have something to eat. >> reporter: would you do this on your own body? >> i would. >> reporter: you haven't done it on any of your family members have you? >> well so far i have no volunteers. >> reporter: when we come back -- what is it like, living with a hard plastic patch stitched to your tongue? >> reporter: 30 days on america's most extreme diet. >> reporter: cheeseburger. i don't care if it's a bite. i just want a burger. >> reporter: will one of these women wish they had never done it? and will the weight come off? sta

dr. rob huizenga points to studies that show most extreme dieters, who lose weight rapidly eventually gainl back and more. marlene doesn't need a study to convince her, she's getting all the data she needs from her bathroom scales, as the pounds fall away. >>> my double chin is not as bad, my arms are a lot thinner. >> lysander is also watching the pounds melt away. >> so far i lost 15, 16 pounds. >> reporter: the final tally marlene loses 18 pounds. lysander loses 23 pounds. >> i don't want to go through that again. it was really hard for me. >> reporter: look at you, you're smiling. >> i would do it again. >> some tough questions from cecilia, more of her reporting on this extreme diet, how much more weight was lost and the cost and the woman who tried something else, avoiding the mirror for an entire year. 20/20 mirror mirror, new year's resolutions tonight here on abc. at 10:00 eastern. when we come back this evening, the stunning sight over america's heartland leaving so many wondering, what was it? t? o many wondering, what was it? the energy in one gallon of gas is also enough to ke