Maria Kang, 32, of Elk Grove, became the target of both admiration and criticism online for her picture, which depicted the woman showing off her physique in short shorts and a sports bra with her three young sons and bore the caption, "What's your excuse?" The Sacramento Bee reported Friday.
Facebook posters and bloggers have accused Kang of "fat shaming" by indicating that other mothers should look like her.
"You, as a woman, should be ashamed that you are furthering the downward spiral of how society views women, and how we women view ourselves ... Most REAL moms don't look like you, sweetheart," Theinklingsoflife.com blogger Morgan Moss wrote.
Kang said she did not mean to insult anyone with the image, which she said was meant to promote her fitness classes.
"I'm sorry you took an image and resonated with it in such a negative way. I ... had an eating disorder, work full time owning two businesses, have no nanny, am not naturally skinny and do not work as a personal trainer," she said in response to her critics. She said her message was that women should "make no excuses not to follow through on your fitness action plan."