Kylie Jenner's Black Friday Insta ad/post has us working up a sweat. "Post thanksgiving in my much needed...new sweat belt," the 18-year-old posted, urging her fans to follow her lead. Of course, Jenner isn't trying to lead a fitness revolution; she's trying to sell sweat belts, a.k.a. waist trainers. She's following in the footsteps of her older Kardashian sisters, who have hawked their fair share of the exercise corsets via Instagram, as well. But this type of celebrity product endorsement promotes a couple of ideas — and genetically unrealistic beauty ideals — that would be healthy to abandon for the new year. First up, Jenner's sweat belt isn't "much needed" to help her magically melt away all those mashed potatoes and pumpkin pie. Because it can't. As we've noted before on Refinery29, many doctors and medical researchers are skeptical at best of claims that wearing corset-like bands can produce their promised results. “All you’re doing is compressing your stomach and pushing the fat around instead of getting rid of it. It’s a very temporary thing,” Dr. Sunil Sharma, director of bariatric surgery at University of Florida Health, Jacksonville, told Ebony. In a 2014 feature examining how waist training really affects the body, Dr. Sharma told the magazine, “Would you be able to obtain fat loss after taking it off? I doubt it.” Nor will wearing Jenner's sweat belt miraculously give us all Kardashian curves. Genetics determine how hourglass our bods will be. Attempting to permanently resculpt our silhouettes could injure our insides. Health magazine broke down a laundry list of potential sweat belt side effects, including acid reflux, constipation, and even acne. Back over at Ebony, Nicole Florence, MD, co-director of Memorial Weight Loss and Wellness Center at Memorial Medical Center, warned that excessive waist training could restrict breathing and potentially bruise ribs. Meanwhile, our collective fears about packing on hard-to-lose pounds in November and December are likely overblown, as Refinery29 explained leading up to Thanksgiving feasting. Studies have found typical holiday weight gain is around a pound — not the eggnog-filled spare tire we're conditioned to fear this time of year. And if you want to shake it off, try sweating the old-fashioned way, no bogus elastic belts required.