You don't have to get a burrito at Chipotle. Try my salad recipe:

Salad with no dressing (you don't need their sugary dressing when you have salsa).

Black or pinto beans.

Optionally, a bit of brown rice, but they will give you too much unless you ask for only a sprinkle of it.

Onions and peppers.

Chicken or whatever meat you like.

Corn, pico de gallo, and medium salsa.

Guacamole. "I know it's extra."

And some of the chopped lettuce at the end of the line, especially if you're getting it to go. "So the guac doesn't stick to the lid."

Now you have mostly vegetables, some meat, some beans, and not much in the way of grains. And it makes two full meals!

The single most popular fast food in Berlin is Döner Kebab, which is about 40% fresh vegetables, 25% bread, 30% grilled meat and some sauce/spices.

It's not super unhealthy as fast foods go.

https://upload.wikimedia.org/wikipedia/commons/9/94/Doener_K...

Fast food is engineered to hit all the sweet spots that our primate brains desire. No matter how delicious my asparagus or salad can be it's difficult to compete with a Quarter Pounder.

My thought experiment of a chain wouldn't directly compete with people choose McDonald's every single time. It'd be for people who've seen the light, and know you can't eat McDonald's, sustainably, indefinitely. That population isn't everyone, but there's a sizable number of consumers who are diet conscious. That's the target market. While McDonald's food is designed to have a certain effect on your palette, you haven't appreciated a skilled cook's entrees if you think there's no realistic competition. Deep, rich, meaningful flavor could absolutely compete against the engineered taste of McDonalds.

There's an Australian chain that does vegetables in the "fast food" format (they have a presence at highway service centres, that sort of thing). So I think you might be right about there being an unserved market for this. ( https://www.oliversrealfood.com.au/pages/our-menu )

I find Cava's green and grains bowl to be pretty good for getting a decent serving of veggies. I usually skip the spreads and dressings and it basically turns into a tasty salad with rice.

They aren't impossible to find, there are loads takeaway sandwich stores as well as buritos. You just have to look a little further than takeaway that has a drive through.