Order Up: As Fast Food Continues to Turn Vegan, What's Next? Vegetarian in 30 minutes or less: how quick service restaurants are diving headfirst into the plant-based food space.

Last summer, while Subway was taking heat for the allegedly mysterious contents of its tuna sandwiches, Long John Silver's used the moment to soft-launch its new, intentionally fish-free items. The fast-food seafood chain partnered with Good Catch, a plant-based fish alternative brand, to sell fish-free filets and crab-free cakes at select locations.

Good Catch's marketing was aggressive. Last July, it parked vans and trucks in front of Subway locations in the U.S. and U.K. and offered free fishless sandwiches. They were made with Good Catch's flaky but fishless tuna, created from a blend of legumes. The clear message was: Here's food you can trust.

But this was much more than just a fish fight. It was a very public example of a shift that's taking place in the way people eat — and therefore, the food that restaurants serve. Plant-based foods are on the rise, and they may prompt a larger shift in the food industry.

Related: Frozen Sandwiches, Wraps, and Pockets are Delivering Flavor Without Meat

Long John Silver's is hardly the first quick-service restaurant to experiment with plant-based alternatives, often by partnering with the brands that are already on grocery store shelves. Burger King started selling the Impossible Whopper, its classic burger made with a meatless patty by food-tech star Impossible Foods. White Castle started selling Impossible Sliders about a year earlier to rave reviews, and it continues to do so. Starbucks sells a sausage-style breakfast sandwich made with Impossible Foods patties. Del Taco sells Beyond Tacos made with Beyond Meat. And there are many more.

Skeptics may have dismissed this trend a few years ago, but the shift clearly has staying power. The meatless alternatives serve vegetarians who want a quick, filling meal as well as omnivores who are making decisions based on health or environmental concerns. It really is remarkable: Not too long ago, it was nearly impossible to find tasty and filling vegetarian food on the road or in small towns. Now, it's a given.

Perhaps we shouldn't be surprised. For decades, we've been told ad nauseam about the health risks and potential dangers of fast food. But despite our culture's growing anxieties about healthy and environmentally friendly eating, we're not abandoning fast food. Not by a long shot.

Related: Plant-based Meat Has Officially Reached 'Global Phenomenon' Status

Instead, we're watching the industry change with the culture. Last summer alone, national chain Little Caesars teamed up with Field Roast to offer the brand's plant-based pepperoni as a pizza topping, and Panda Express debuted orange chicken from Beyond Meat. Throughout the food industry, leaders continue to test out new products and ideas that bridge the gap between our favorite comfort foods and our more modern concerns.

These companies are wise to do so. Roughly 4% of Americans self-identify as vegans, which is a substantial leap up from 0.4% in 2017, and the market for plant-based food is even larger because of the number of Americans increasingly interested in eating this food. Sales of plant-based foods are now
$7 billion annually, and are growing at a rate more than twice that of total food sales. Whether fast-food chains are driving the growth of plant-based food brands or simply capitalizing on a trend that's already in motion, it's hard to say. But this much seems clear: The growing interest in meat-free foods presents an opportunity for larger brands to expand their menus, as well as for smaller brands to lean more heavily into an underserved market.

Related: Thinking Outside the Box: How Vegan and Vegetarian Brands Are Reinventing Frozen Pizza