Russian-born tennis player Anna Kournikova is joining the television weight loss contest "The Biggest Loser" as a trainer, NBC television said on Wednesday. Kournikova, 29, who became a sensation on and off the courts despite never winning a major singles tennis title, will join the show in September. Born in Moscow and now an American citizen living in Miami, Kournikova said she had long been a fan of the TV show, in which overweight contestants attempt to lose the most weight through diet and rigorous exercise programs for a cash prize. "As a former professional tennis player and certified trainer, this is a wonderful opportunity for me to share my enthusiasm for staying fit across America's homes," she said in a statement. NBC reality show chief Paul Telegdy said the network was "confident that she will be a powerful motivator to contestants to get fit and healthy." Kournikova started playing tennis competitively at the age of eight and made her Grand Slam debut at 15 at the U.S. Open. She won Grand Slam doubles titles with Martina Hingis in 1999 and 2002, but was equally famous as a model and for her romance with pop star Enrique Iglesias.