Experts Explain How TikTok’s Viral Leggings Make Your Butt Look Like That

In November 2020, a specific pair of leggings sold by a French company Seasum for $25.99 went viral overnight, thanks to the popular hashtag #TikTokMademeBuyIt, which encourages users to try out items and hacks. The style, featuring a honeycomb-like texture and an indentation on the lower back that simulated a pulled-up thong, was lauded by users for its comfort. But what truly sets these leggings apart from the millions out there was its unique ability to transform anyone’s derriere. One of the first users to share them was Lauren Wolfe, a TikToker with over 500,000, who claimed that her “butt does not look like that” normally. The video now has over 250,000 likes. 
Since then, the hashtag #TikTokLeggings has garnered over 630 million views on the app, 60k reviews on Amazon, and “booty-lifting” dupes from other brands. Even Lizzo is a fan. Picture a pair of leggings that mix the comfort of activewear with the appeal of shapewear, featuring an intentional wedgie that carefully separates your buttcheeks, giving anyone a derriere made for its own reality TV show.
For months now, the success of the TikTok leggings has puzzled shoppers who want to understand how regular butts become superbutts in them. The company claims that the key to its “butt lift” comes from a four-way stretch fabric that “conforms and contours with each pose and movement.” But is that actually what’s going on? 
Textile expert and assistant professor of textile development and marketing at the Fashion Institute of Technology Preeti Arya doesn't buy it. Arya says that the technique used in these leggings is “west knitting,” the most common type of yarn technology used today, mainly because it allows the garment to stretch even if the fabric doesn’t have elastane. On Seasum’s website, the leggings are described as having a “special mesh textured fabric,” which Arya says may be “just a modification” of regular west knitting that allows for a textured appearance, altering the shape of the legs to look more full. 
Although the company highlights the “textured fabric” as one of the signature factors for the leggings’ “butt-lifting” capabilities, textile expert Preeti Gopinath says there’s no lifting happening at all. Instead, it's about the design, which draws attention to the wearer's butt crack. “It’s very rare that you find leggings that have that ruching at the [back] seam,” says Gopinath, who’s the director of the masters of textiles program at Parsons The New School for Design. As opposed to regular leggings, which Arya notes are typically sewn in a way that allows the seam to sit “right on top of the butt line,” these Seasum leggings gather fabric from within the butt-crack to define the two cheeks, giving the illusion of a derriere so big that it's stretched out the legging's fabric. The V-shape waistline in the back also exaggerates the scrunching at the seam. Arya calls the Seasum version “a genius design.”
While it seems the whole cyberspace has tried the leggings, not everyone is a fan of them, especially people who wear them to work out. Some user reviews describe the backside seams ripping open, or stretching out to create holes. At the end of the day, clever design can’t compete with an actually powerful butt and its movements. 
The activewear boom is a key factor to understand why these leggings went viral. Before the pandemic, activewear had already been on the rise, with brands like Lululemon, Athleta, and Outdoor Voices leading the market, valued at $155.2 billion in 2018, according to ReportLinker. It’s expected to hit $547 billion by 2024. TikTok is also ripe for items like these to go viral, fostering communities where niche trends and products are becoming the new mainstream. 
Neither Arya or Gopinath believe the leggings are particularly magical. Instead, they point to the triple-threat construction — textured knitting, scrunched back side seam, and dipping waistband —  as giving the appearance of a lifted backside appearance, rather than actually lifting it. Arya says, the real body part these leggings affect isn't your butt, but rather your brain: “It’s all an optical illusion.”

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