Trainer Chris Powell (R) coaches a man on US reality TV show "Extreme Makeover: Weight Loss Edition" in this undated 2011 handout. [Photo/Agencies]

New York - Chris Powell, trainer for the US reality TV show "Extreme Makeover: Weight Loss Edition," may hold a degree in exercise science, but he says his business is transformation.

That jibes nicely with his role on the series, where he serves alternately as coach, drill sergeant, cheerleader and shoulder to cry on to desperately obese people struggling to lose fully half their body weight.

"Super obese is actually the technical term for the individuals that I work with," Powell, who calls himself a transformation specialist, explained, "individuals with over 200 pounds (91 kilos) of extra fat on their bodies."

Each episode follows one individual's year-long metamorphosis.

The 33-year-old Arizonian has been working with the super obese since 2003.

"There's something so magical about this group because they are the group that the cards are stacked against," he said.

While the TV transformations are dramatic, Powell said the methods can work just as well for the couch potato who needs to drop 20 pounds.

"From a diet and exercise standpoint, losing 20 or 200 pounds is almost identical. It's just scale," he said. "The beauty of working with the super obese is that if they make one tiny change, like switching from cola to water, they see huge changes on the scale."

He also explained that because they have developed the muscle to accommodate their girth, a little movement goes a long way.

"They're sitting on huge metabolic engines and they don't realize it," he said." If I just tell them to move 10 minutes, their calorie burn is through the roof."

Powell, who has also studied biomechanics and physiology, describes his fitness philosophy as "a little of this, a little of that."

But whatever your goal, switch it up and pick it up.

"On the show everything is turbocharged," he said. "Once they've cleared the medical (examinations), I push them. That very first workout is grueling. Constant overloading is the only thing the body responds to."

He's also a firm believer in interval training.

"Intermittent high- and low- intensity exercises in a randomized pattern get so much more out of the body," he said, "and it's an opportunity to experience relatively high intensity for short durations."

Powell works with therapists to ease participants' transitions into their new bodies.

"They're taking on a whole new identity. It's stressful, even though it's a positive stress."

So between bouts of self-pity over fried food deprivation and tears of exhaustion on the treadmill, participants are buoyed by dream vacations and what Powell calls "superman moments."

Halfway into one episode, Powell urged Rachel, a 21-year-old school teacher, to experience her new body by bungee-jumping off the Bridge to Nowhere in California.

"It changes your identity,"  said Powell, who encourages those without a network television-sized budget to create more modest milestones, like running a marathon, or a mile.

Powell said he's a veteran of his own transformation, albeit from the opposite end of the scale.

"I was the smallest kid in school, so I had fair share of bullying. It was not easy, but my parents bought me my first weights and I felt empowered for the first time. It changed my life."

Meanwhile, bungee-jumping Rachel dropped some 200 pounds and is working towards her personal training certification.

"About half of the people I've transformed are working toward their certifications right now," Powell said. "They're loving it."