Fast-fashion brands are taking steps to clean up their act.

It’s no secret that, by nature, fast fashion isn’t doing the environment any favors. For years, brands like H&M, Zara and Forever 21, and, more recently, the Fashion Novas and Boohoos of the world, have been making a profit by taking runway trends and quickly recreating them for the mass market at a fraction of the cost. Their products are designed to be worn once or twice and then thrown away, contributing to the already massive amount of clothing that is discarded. Roughly 85% of textiles end up in landfills, per the United Nations.

But as younger consumers shift their focus to brands that celebrate radical transparency and environmentally friendly practices, like Reformation and Everlane, fast-fashion brands are having to backtrack and think more about the impact they’re having on the world.

“There’s been a 130% increase in Google searches on sustainable fashion in the last year, so there’s clearly a growing interest in this area. That’s part of the reason fast fashion is going along with the general trend — because they have to. That’s the way the consumer is pushing them,” said Diana Smith, Mintel associate director of retail and apparel.

In 2017, H&M pledged to use 100% recycled materials and other sustainably sourced products to make all of its products by 2030. At the end of 2018, 57% of the materials used by H&M were recycled or sustainably sourced. Zara, on the other hand, pledged to stop sending unused textiles to landfills by 2020, and started using some sustainable materials in 2016.

“Our sustainability vision is to use our size and scale for good and, with the help of technology and innovation, to lead the change toward circular and renewable fashion, while being a fair and equal company,” a spokesperson for H&M said. “This vision is not only necessary from a social and environmental perspective, but it also makes good business sense.”

But while fast-fashion companies are taking these steps to improve, the question remains whether they can truly be sustainable if their business models are built on high-production volume and low costs.

Loose Threads founder and lead analyst Richie Siegel said a big question for consumers and analysts should be whether these companies can actually deliver on their promises. “There is probably a way — with a lot of work, recycling, repurposing, up-cycling — where you could make improvements in this existing fast-fashion model, but generally speaking, that model is an unsustainable model,” he said.

To be truly successfully sustainable, Siegel said brands like H&M and Forever 21 would need to accomplish a number of things: One would be to use less harmful practices to make product, which many are starting to do. Another would be to recycle more and, finally, encourage consumers to buy fewer new items and instead opt for used items.

The H&M group’s & Other Stories brand has an in-store recycling program (H&M has one as well) where shoppers can bring in empty beauty packaging and pre-worn garments and textiles. The brand also got into the secondhand market earlier this month, launching a trial program with online marketplace Sellpy to sell some & Other Stories second-hand merchandise. The group plans to extend this idea to all of its brands, including H&M, in the future.

“A true sustainable company would work on all of those dimensions, not just one of them. That’s hard, and it’s often expensive,” Siegel said.

While some see fast fashion’s venture into sustainability as an uphill battle, Smith said she commends these brands for starting somewhere. The work involved in converting some of these multibillion-dollar companies, built on fast and cheap practices, into more eco-conscious ones can’t happen overnight. Taking steps to implement new brand goals and teaching consumers about those practices is key for a brand like H&M, she said.

“H&M’s efforts are really commendable, because their recent initiatives are designed to change the consumer mindset. They’ve trained consumers how to buy low-price, throwaway fashion, and now they are encouraging consumers to pay attention to a different kind of fashion consumption, one that is more sustainable,” Smith said.

Both Smith and Siegel said intention will play a key part in determining which fast-fashion brands will be successful in this space. Brands will need to prove that they are in this for the long run, and not to just make some quick cash from one-off sustainable collections and gain some good PR. Some brands try to hop on the sustainable bandwagon by launching an eco-conscious line of clothing, while others use it as a way to test the waters and see if it’s something their customers are interested in.

Take Pretty Little Thing, for example. On April 18, the U.K.-based fast-fashion retailer launched a small recycled fashion line featuring staple pieces like cropped hoodies for $32 and leggings for $22, both made from used and unwanted garments. While the line is just a small fraction of the brand’s massive inventory, it’s still a start. The company, which reported revenue of $338 million in 2018, did, however, recently partner with clothing recycling app Regain to help cut back on the amount of clothing going into landfills. Pretty Little Thing did not respond to a request for comment.

“I would fully encourage experimentation. Doing something is better than doing nothing, but one has to be realistic of what the real impact is with something like that,” Siegel said.