7 up-and-coming healthy fast food chains that should scare McDonald's

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 November, 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 even 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 around the same price. Though these new US chains are regional, they're growing in popularity, so they could spread nationwide in the coming years.

Check them out below.