Kournikova joined the show last September.
"I enjoyed my time on the 'Biggest Loser' ranch," the athlete said in a statement issued to EW.com. "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."
Benedict Cumberbatch's dramatic reading of R. Kelly lyrics is just what you need
Gal Gadot cast as Wonder Woman for 'Batman vs. Superman'