You've probably heard of waist trainers. They're the somewhat controversial celebrity trend popularized by stars like Kim Kardashian and Kylie Jenner, who wear them during their workouts to achieve tinier waists. Some critics say it's bad for your health (and squeezes your organs), but judging by these before-and-after pics, the results speak for themselves.

Don't Be Tardy's Kim Zolciak-Biermann is a big fan of waist training and has posted plenty of photos on Instagram of her amazing success.

MUST SEE: Khloé Kardashian, Demi Lovato, and More Stars Whose Gym Selfies Are an Excuse to Show Off Their Butts

“A waist trainer will help you get the figure you want and feel sexier and better about yourself,” she said on Good Morning America. "I wear it four to six hours a day, every day, and that's it. Some people wear it to bed. I don't wear it to bed; I want to be comfortable."

The reality star even disputed claims that the results are only temporary. “I didn't wear it for seven days while I was on my honeymoon and my body didn't go back,” she said.

Click through the gallery to see before-and-after pics of celebrities wearing waist trainers.