It's been about a year since Kim Stringham, of Holladay, enlisted in a Bootcamp with Jess fitness program.

She's lost 30 pounds.

Matt Stoker, meanwhile, knows he can no longer eat his wife's homemade cookies until he loses some extra pounds. His instructor, Jess Thomas, will make him pay in push-ups.

"I don't want them to waste my time or theirs," Thomas explained during a recent interview at his Salt Lake-area gym, one of five Bootcamp with Jess franchise locations.

It's a blunt statement and a tough stance, but for Thomas, it works. He's developed a thriving fitness program based around a no-nonsense, military-type approach to workouts.

The whole goal is to help people change habits and improve fitness. And Thomas, a former military man, has achieved a 97 percent retention rate.

For Jennifer Camp of Millcreek, the program works because someone is in complete control of her workout.

"I just wanted something that would kick my butt," she said during a recent morning workout. "I've been out of shape a long time."

Another participant, Trish, of Holladay, said the program has motivated her to get moving again. She's lost three inches off her waist and said she loves the program.

And while Thomas may look intimidating, Trish said he's a "real nice guy."

"He probably doesn't want me to say that," said Trish, who asked her last name not be used.

People of all fitness levels can sign up for the program, which runs in six-week sessions with classes five days a week. The first time a person signs up for a session they are required to don a weight vest for a week and participate in what is known as "hell week."

After that first week, the weight vest comes off.

It's designed to challenge participants mentally and physically, according to Thomas. But trainers do tailor workouts to individual fitness levels. People with asthma, cancer and excess weight have successfully made it through "hell week," according to Thomas.

For him, the program is about helping people make a change.

"If they don't change, I have a horrible name," said Thomas, the CEO and founder of Bootcamp with Jess. "It's my name. It's my reputation. Here, I want them to re-enlist."

E-mail: nwarburton@desnews.com