The photos show Hewitt, with a bit of cellulite, on a Hawaii beach with her new fiance, Scottish actor Ross McCall.
Several sites posted the shots, along with some less-than-complimentary comments. TMZ.com, for example, said, "We know what you ate this summer, Love everything!"
"A size 2 is not fat! Nor will it ever be," Hewitt responded in a post Thursday. "And being a size 0 doesn't make you beautiful."
"What I should be doing is celebrating some of the best days of my life and my engagement to the man of my dreams, instead of having to deal with photographers taking invasive pictures from bad angles," says the star of TV's "Ghost Whisperer" and the film "I Know What You Did Last Summer."
"To all girls with butts, boobs, hips and a waist," she wrote, "put on a bikini put it on and stay strong."
