Planet Fitness, Newington, NH, opened its 500th club on Monday in Morton Grove, IL, the company announced.

Planet Fitness, which opened its 400th club in February 2011, plans to open more than 100 new facilities in 2012. The company began franchising in 2003 when it consisted of four clubs in New Hampshire.

“I thought at the time that maybe we’d end up the biggest loser,” Planet Fitness CEO and co-founder Mike Grondahl said in a statement. “But 500 gyms ain’t half bad.”

In some ways, the company did end up the biggest loser. As Club Industry reported last October, Planet Fitness now has a national partnership with NBC’s “The Biggest Loser.”

During this season, contestants on “The Biggest Loser” will work out on fitness equipment given by Planet Fitness at The Biggest Loser ranch in Calabasas, CA. In some episodes, contestants will work out at Planet Fitness gyms near their homes under the guidance of Planet Fitness trainers.

Planet Fitness was No. 7 on Club Industry’s Top 100 Clubs list in 2011 with a reported $157.1 million in 2010 revenue. The company boasts more than 3.5 million members in the United States and Puerto Rico.