EDISON PARK — Kevin Pemberton hit rock bottom in December 2010.

He was 16 years old, stood 5 feet, 9 inches tall and weighed 294 pounds.

"I just looked at myself in the mirror and said, 'This has to change,'" said Pemberton, a Norwood Park native. "I just wanted to better my life so I could live longer.

"I didn't want my kids to have that fat dad who couldn't play baseball with them or hang out with them in general," he said.

So Pemberton decided to send in an audition tape to the MTV reality show "I Used To Be Fat", which transforms overweight teenagers with ultra-rigorous training.

Pemberton, 19, was selected and spent the summer of 2011 being taped for 200 hours over 80 days. The footage was broken down to an hourlong episode that aired for the first time July 16 and will be displayed on MTV's website soon.

Norwood Park native Kevin Pemberton weighed 275 pounds when he submitted this audition video from MTV's "I Used To Be Fat". Pemberton, 19, lost 78 pounds on the show. View Full Caption YouTube/Kevin Pemberton

Pemberton tipped the scales at 276 pounds his first day of taping. He finished the show at 198.

A crew of five cameramen and producers followed Pemberton for the 80 days, from the time he woke up to when he hit the pillow for the night. He trained five to six hours a day, on camera with renowned fitness expert Saran Dunmore, who appears frequently on NBC5 and has trained five subjects for "I Used To Be Fat".

"It was tough in the beginning because most people don't like change," said Dunmore, a Morgan Park High School graduate, Beverly native and South Shore resident. "We would do sprints, and he would give up a meter before the finish line. But once he saw those results ... he figured out a way to make it work."

Away from the spotlight, Pemberton spent countless hours with Matthew Roeske, then a personal trainer at The Better You Fitness Studio and now the owner of Chicago Style Fitness in Edison Park. Roeske, who said he's trained more than 1,000 people, said he's never been prouder of a student than he is of Pemberton.

"He just never gave up," said Roeske, 27, who said a highlight was watching Pemberton burn 8,000 calories in one day after 11 hours and 16 minutes of cardiovascular exercise. "I meet a lot of people who piss me off because they quit, and he kept at it."

Roeske said without "I Used To Be Fat," Pemberton would possibly weigh 400 pounds. Pemberton said he might be dead by now.

His routine breakfast used to consist of three sausage biscuits and a trio of hash browns at McDonald's. Lunch would be pizza, fries and whatever leftovers his classmates at Notre Dame College Prep provided.

"Dinner was actually healthy, but that didn't matter," Pemberton said. "I struggled with everything I did. It was hard to do any physical activities, and even though I was good at sports, I was always the last person to finish."

Pemberton now maintains a strict diet, eats turkey burgers and grilled chicken instead of red meat, and has vegetables with every dinner. Heading into his junior year at Southern Illinois University, Pemberton is majoring in exercise science, with a future planned career as a physical therapist.

His family lost weight, too, because of the show. His mother Joyce dropped 17 pounds, her husband, Ward, a Chicago firefighter, lost 30, and their other son, Ryan, lost 20.

"We had to change everything we do in our house," Joyce Pemberton said. "A standard snack used to be nachos, but we cut out all the garbage, and our house is full of vegetables and very lean meals. We are a completely healthier home because of this."

Pemberton, who is now 212 pounds, still works out seven days a week, lifting, running and using elliptical machines. With his "I Used To Be Fat" episode finally airing, he's amped up his regimen and hopes to soon weigh 180 pounds.

Now, when he glances in the mirror, he can't believe his incredible weight -oss story.

"Man, I don't even know how I did it," he said. "I just know you have to have the right mindset. You'd be surprised what you can accomplish."