Glen E. Ellman Tim McCarty, left, works out at the Dallas facility with another member and their trainer

If you live in Chicago or Dallas and have a few pounds to lose, you might spot Downsize Fitness and think you’ll give this new gym a try. Forget it. This is a club that won’t take you as a member—unless you have at least fifty pounds to lose. And they weigh you to make sure.

A gym that rejects the svelte and toned? Could this work? When Downsize’s founder Francis Wisniewski got his brainstorm almost two years ago, he couldn’t believe it wasn’t already out there.

Weighing 360 pounds, the 39-year-old hedge fund manager wouldn’t set foot in a regular gym. He was all too aware that most clubs were filled with “women in tight clothes running 5-minute miles” while he struggled to do 15 minutes on the elliptical machine. “I was also embarrassed about how I looked,“ he said, “and how much I sweated.” His business partner got him a full-time trainer to work with him at home.

In November 2011, a 299-pound Wisniewski opened the first Downsize Fitness In Chicago and in September 2012, another in Dallas. The gym’s program is inspired by the approach used on “The Biggest Loser” reality show, which tailors workout regimens to help overweight individuals drop pounds. Downsize’s stated goal is to help the obese lose weight in an environment where they feel comfortable and free of judgment. A complete membership of $250/month (with a 6-month contract) includes personal training and nutrition counseling in small groups of three to six members. Most trainers know what it takes to shed pounds since they were formerly obese themselves. And while they won’t judge you, they will hold you “accountable.” Skip a few workouts? Expect a call or text to check up on you. Oh, and you can also compete for a prize in the $25,000 weight loss challenge.

Forest McKinney, a 42-year-old audio-visual engineer in Plano, TX, who recently joined the Dallas gym, may be exactly who Wisniewski had in mind. At standard gyms, neither the machines nor the exercises worked for him. At 6’2” and carrying an extra 200 pounds, he couldn’t, for example, do ten jumping jacks. Or even one. “It’s not gonna happen,” he says. “It’s not a healthy or good option for me.” At Downsize, his trainer substitutes leg extensions that give him some of the benefits without the dangers.

This cautious approach to exercise is a better way to go, experts say. “People 50 pounds or more overweight need to take it easy on their bones, muscles and joints until they get their weight under control,” says David J. Dausey, Chair of Public Health at Mercyhurst University. He also endorses the idea of group support. “People are more likely to keep with their regime so that they don’t disappoint their friends.”

“You rely on each other,” says Jack O’Donnell, a plastics manufacturer in Chicago. He credits Downsize with saving his life. In January 2012 at age 53 and 5’10”, O’Donnell was 257 pounds. He took blood pressure medication and 150 units of insulin a day. Now he weighs 176 and takes no medication at all.

Group support is great, says Leslie McKinney, but couple support is critical. She recently joined with her husband Forest, hoping to take 180 pounds off her 6’ 1 ½” frame. She and Forest had found it hard to get on the same page about healthy eating, she says. Now they’re whipping up foods suggested by their nutrition counselor. Quinoa with cilantro and BBQ seasoning was a recent winner. “We can both get on board with this,’” Leslie says.

How important is the prize money? Not very, folks tend to say—until they’re in the running. Tim McCarty, 41, of Dallas, who joined in September 2012, told himself he’d never win. Then he found out he was in third place and upped his workouts to four hours a day. “I’m very competitive,” admitted the 5’3” maintenance man. Not only did he win the top prize of $7,000, but also he shed 85 pounds and his sleep apnea machine. Plus this bonus: he’s been asked to be a Downsize trainer.

In January 2012, a few months after Downsize set up shop in Chicago, Marty Wolff, a former contestant on “The Biggest Loser” decided to set up his own club for “people of size” using principles from the reality show. At Wolff’s Square One in Omaha, members benefit from support groups for food addiction along with individual and group exercise sessions, nutrition classes and social social: at meal swaps, they trade off extra portions of home-cooked food meets program requirements. Membership has swelled to 100 and the gym had to move from its 2500-square foot space to one double that size.

Downsize, too, is expanding — in a good way — to accommodate the demand for its overweight-only focus. Its membership has climbed to 140 in Chicago and 180 Dallas, and its Facebook page is flooded with pleads for facilities in more towns. Wisniewski says he’ll open gyms this summer in Naperville, IL and Fort Worth. He hopes his fledgling New York City boot camp will eventually become a full gym. He’s thinking big in order to help more people slim down.