Basic membership at the gym is $50 a month. A premium membership, which includes a trainer, a nutritionist and unlimited group classes, costs $250 a month.
Some critics say that Downsize Fitness segregates obese people, but Wisniewski believes it is for a purpose.
"Gyms are built for fit people to stay fit," he said. "I don't think they are built for fat people to get fit. In a way, we are segregating, but we are segregating for a reason."
Lewis Cline also joined Downsize Fitness six months ago, when his starting weight was 310 pounds.
He said he tried to lose weight at one of those "other" gyms and was a member for 12 years, paying $75 a month. But after only going for one year, he never went back.
"It wasn't something where I was comfortable going into the gym," Cline said. "You are on your own. There is no one there to help you. There is no one to explain what you should be doing."
Since joining Downsize Fitness, he has dropped 50 pounds and his goal weight is 180.
Exercise physiologist Jennifer Ventrelle agreed that it makes a difference to be comfortable when deciding to engage in healthy behavior.
"It's not about, 'Oh, it's OK that you're big. You can stay the way that you are. It's OK that you are not physically active because you don't feel comfortable in the gym,'" she said. "You're going to be working just as hard. It's just in a different environment. You're being more accommodating to someone so that they can engage in healthier behaviors."
Chris Almaguer is Downsize Fitness' biggest success story. The first day he entered the gym, he weighed nearly 500 pounds. Just one year later, he has lost a whopping 202 pounds. His goal weight is to get to 190.
"It was more like this, I was just trying to hold myself up and my back was just hurting too much," he said.
He is now one of the gym's most active members.