Capt. Andrew Neiman of the Los Angeles Police Department told the Los Angeles Times in July that a criminal investigation was opened after LA Fitness officials reported the image as "illegal distribution."
"If I can't unsee this then you can't either," Mathers wrote on the photo. She also posted a photo of herself covering her mouth in apparent disgust.
In response, LA Fitness banned Mathers from all LA Fitness locations nationwide.
"Her behavior is appalling and puts every member at risk of losing their privacy," said Jill Greuling, LA Fitness' executive vice president of operations. "Our written rules are very clear: Cellphone usage and photography are prohibited in the locker rooms. This is not only our rule, but common decency."
Mathers later apologized on Twitter and Snapchat.
"I have chosen to do what I do for a living because I love the female body and I know that body shaming is wrong and that's not what I'm about," she said. "That photo was taken to be part of a personal conversation with a girlfriend and because I am new to Snapchat, I really didn't realize that I had posted it and that was a huge mistake."