Did Biggest Loser star Tara Costa gain the weight back? FC Online Marketing Inc. has filed a lawsuit against the reality star, claiming she didn't maintain her weight loss as part of a business deal between them.

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"We hired Tara Costa in 2011 to be a spokesperson," FC chief executive Michael Parrella told Newsday. "She came on at a certain weight. We had a fitness clause. She was in material breach after she gained, in my opinion, about 45 pounds. She was supposed to visit 15 of our franchise locations, but we weren't able to send her anywhere because she gained a lot of weight." FC, which owns ilovekickboxing.com, had hired Costa to make public appearances.

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But Costa and her lawyer, Darren Heitner, have vehemently denied the allegations.

"This case has absolutely nothing to do with Ms. Costa's weight and everything to do with FC Online's breach of an appearance contract, along with their exploitation of Ms. Costa's name and image without compensation on a website that promoted their commercial services," Heitner told TODAY.com. "Since appearing on season seven of NBC's hit series, The Biggest Loser, Ms. Costa has remained physically fit and even participated in an Ironman competition. FC Online's effort to frame any debate as one related to Ms. Costa's appearance is misguided and will be exposed throughout the litigation." 

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Costa, who came in second place on The Biggest Loser in 2009, also argued on Twitter that she was actually in her best shape at the time the suit refers to because she competed in the 2011 Ironman World Championships in Kona, Hawaii.

To further prove her point, Costa has been posted full-body photos of herself showing off her slim, toned body while working out. "Transformation Tuesday!" she captioned a before and after shot of her appearance on The Biggest Loser compared to present day. "4 years later . . . I'm proud!"

This article originally appeared on Usmagazine.com: Tara Costa, Biggest Loser Star, Sued for Alleged Weight Gain