A doctor and fitness trainer weigh in on the modern-day corset, a favorite Instagram topic for the Kardashian clan.

Another day, another Kardashian promoting waist-training devices on social media. This time it’s new mom Kylie Jenner, and she’s touting the corset-like products as a way for women to “snap back” after giving birth.

“My girl @premadonna87 hooked me up with the @waistgangsociety snap back package,” Jenner wrote yesterday in a sponsored Instagram post. She then encouraged her followers to purchase the package using her exclusive discount, so she “can keep up with your progress.”

We’re all for empowering new moms (and losing weight with friends!), but we’ve got a few issues with what’s going on in this post. To begin with, the notion that women can or should “snap back” to their pre-baby bodies isn’t the healthiest. And on top of that, the idea that a waist trainer can help is, well, questionable at best.

If you’re new to the waist-trainer world, here’s a quick primer: These modern-day corsets are essentially thick bands of material that wrap tightly around the waist and lower rib cage. Kylie’s sisters Kim and Khloé have both promoted them on Instagram, and celebs like Jessica Alba and Brooke Burke-Charvet have credited waist training for helping them get back in shape after childbirth.

There’s no question that, while you’re wearing them, waist trainers deliver a slimming, hourglass look. Companies that market waist trainers also claim that the devices can reshape the body or reduce belly fat—but Carolyn Apovian, MD, a professor of medicine at Boston University School, previously told Health that “in my opinion, that is complete nonsense.”

Dr. Apovian says there’s probably nothing wrong with wearing a waist trainer for the sole purpose of looking thin for a few hours. “If you look in the mirror and like what you see, it can potentially be a good thing,” she adds; it may even boost a woman’s confidence and encourage her to exercise and eat healthy.

But a waist trainer won’t change the shape of your body, she says, and you won’t see lasting effects once you take it off. In fact, celebrity trainer Nicole Glor told Health, regularly wearing a waist trainer might actually decrease core strength. (A better goal, she says, would be sculpting lean muscle with moves like planks and twisting crunches.)

As for new moms, Dr. Apovian says that wearing a waist trainer during workouts may help women feel more comfortable, as long as it’s not so tight that it restricts breathing or causes discomfort. "If it helps everything feel a bit tighter and there's less jiggle around your stomach,” she says, “it may help you feel better about exercising."

But women should still follow their doctor’s advice about how much and how hard to push themselves as they start exercising again—and they shouldn’t feel pressure to "snap back" too quickly. And while some waist trainers claim to reduce water retention and swelling of the uterus, Dr. Apovian says that’s not true.

"The uterus is going to shrink when it feels like shrinking," she says, "and you can't get rid of water weight with a corset—that's simply not true."

There could be risks, as well: If waist trainers are too tight, they can interfere with breathing or contribute to heartburn. "Your stomach might get pushed up beyond the diaphragm, which could cause reflux," says Dr. Apovian. "If you're wearing one and you experience those symptoms, that's a definite sign that you need to loosen it or take it off."

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We’re not the only ones who noticed something off about Kylie’s post. Many of her Instagram and Twitter followers were quick to criticize the star for hawking a product that (a) isn’t proven to actually do anything and (b) could perpetuate negative body image among her followers—including teenagers and other new moms.

Instead of waist training, we’d love to see Kylie promoting healthier and more effective ways for new moms to lose the baby weight—when they’re good and ready, that is—like following a balanced diet, starting a postpartum exercise routine, and yes, even breastfeeding. Not only are these strategies actually proven to help shed unwanted pounds, but they come with lots of other benefits, as well.