(NEW YORK) -- A year ago, Nick Preto, a 16-year-old from Baytown, Texas, weighed an astounding 403 pounds. He was about to enter his senior year in high school and was plagued with potentially life-threatening health problems.
ABC's Nightline asked Preto and his mother, Toni Preto, if they could follow him as he underwent a highly controversial surgery for teenagers: gastric bypass.
Over the course of the past year, Preto has gone on a remarkable weight-loss journey, losing 150 pounds and changing the way he lives his life. But it has not been easy.
Last June, before the surgery, Preto took Nightline on a tour of the fast food joints he regularly visited. He was routinely consuming 7,000 calories a day -- three times the recommended total for an adult man -- and knew he had to make changes.
"It's senior year, you know, you want to date the homecoming queen. You want to have the cutest girl," he said at the time. "I guess just because I've been bigger, nothing has really happened with ... the ladies."
But Preto's doctors told him if he didn't lose the weight, the ladies were going to be the least of his problems. The teenager was careening towards an early death. He was already a pre-diabetic and suffering from sleep apnea, liver damage and joint pains. So he decided to get some radical help through gastric bypass surgery.
Preto's surgeon, Dr. Mary Brandt, was hesitant about doing such a major and irreversible operation on a teenager.
"I really didn't think it was a good idea," she said. "I mean, metabolically changing someone who's a growing adolescent to me, made no sense. But this is the first generation that's not going to outlive their parents. That's the scariest thing to me."
The procedure, which completely rewired Preto's digestive system and reduced his stomach from the size of a small toaster oven to the size of an egg, took about two hours. The first weeks after surgery were tough for Preto as he adjusted to eating tiny portions.
Seven weeks later, his weight was down from 403 pounds to 315 pounds. But Preto told Nightline anchor Cynthia McFadden that changing his diet was difficult. Not only was he frequently vomiting, the whole process had been an emotional roller coaster.
But despite the tough road, Preto was determined to keep going, and said he intended to lose 100 pounds in the next six months.
Nightline reconnected with Preto a few weeks ago after the six months was up for the big weigh-in. When he stepped on the scale, he had dropped another 70 pounds, which was not quite the 100-pound goal he had set for himself, but still an impressive achievement, weighing a total of 247 pounds. A year ago, his waist was 60 inches. Today, it's 34.
But more important than the number on the scale was the joy in Preto's eyes as he stepped out to attend his senior prom with his new girlfriend, Jordan. Not only was he healthier, he was happier too.
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