Tennis star Anna Kournikova won\'t be returning to The Biggest Loser. Kournikova was one of two trainers brought aboard to join Bob Harper after Jillian Michaels left the show last season. Known for her glamazon good looks, she struck some as a curious choice. But Kournikova said she had plenty in common with the obese contestants on NBC\'s reality weight-loss show: Years in the media spotlight left her struggling with feelings of inadequacy and insecurity about her looks.However, her tenure got off to a rocky start. This season\'s theme is Battle for the Ages, pitting youth against oldsters. Kournikova ended up with the senior set, and they have struggled, losing several weigh-ins and challenges.Moreover, she created conflict with several of the players — and made no friends with viewers — with a less-than-sympathetic demeanour.Hollywood Reporter, which broke the news about Kournikova\'s departure, hinted that Kournikova was clashing with folks on and off camera. Representatives for the show and for Kournikova were unavailable for comment. The Hollywood Reporter said Kournikova gave no reason for the departure beyond wishing everyone well: \"I enjoyed my time on the Biggest Loser ranch. Although I will not be returning as a full time trainer on season 13, I will always be a part of The Biggest Loser family and my commitment to bettering lives through health and fitness will continue.\"