Legacy mega-brands like McDonald's, KFC, and Burger King have dominated the fast food industry for decades.

But within the last few years, many American consumers have shown a growing interest in healthier fast food that incorporates more low-calorie ingredients and fresh produce while remaining convenient and affordable.

In late 2016, top food executives from PepsiCo and Campbell Soup Company told Fortune that cleaner food is not just a trend, but a movement. And that shift is spilling over into the fast food market too, forcing legacy chains to try to keep up. In the last four years, Taco Bell has pledged to cut artificial ingredients and use cage-free eggs, and has introduced a lower-calorie menu. McDonald's has worked with dietitians, removed antibiotics from its chicken, and added more salads to its menu.

But new healthy fast food chains are also seizing the opportunity to compete with legacy brands, creating low-calorie menus for similar prices. These new chains are regional (for now), but they're growing in popularity.

Check them out below.