More than 160,000 people are petitioning McDonald’s to add a vegetarian protein option to its menu across the US – just as it added the “McVegan” internationally.

Although the petition does not specify which kind of veggie burger activists would like, it comes on the heels of an announcement from Burger King that the chain is testing a plant-based Impossible Burger patty for its Whopper (calling it the “Impossible Whopper”).

“I’m hoping to bring a positive change to America with a mainstream meatless option at McDonald’s!” wrote Kathy Freston, author of the petition and a vegetarian activist. “Healthy living should be about progress, not perfection, and this is an easy step that McDonald’s could be taking.”

McDonald’s does not have a broadly available vegetarian option in the form of a burger in the United States, although some of its sides appear to be vegetarian. However, the company’s website says it does not “promote any of our US menu items as vegetarian, vegan or gluten-free”.

In December, McDonald’s introduced the McVegan to the menu at its Chicago headquarters, after a trial in Finland and Sweden. The patty is “reminiscent of samosas”, according to the beef industry publication Drovers.

Also in December, McDonald’s senior vice-president of corporate strategy Lucy Brady told Fortune: “Plant-based protein is something we’re keeping our eye on,” referring specifically to meat replacement startups like Impossible Foods. McDonald’s did not respond to a request for comment by the Guardian.

The Impossible Burger, the patty introduced at Burger King, is best known as the veggie burger that “bleeds” thanks to the addition of yeast genetically modified to produce the protein heme, a compound carried in blood cells as hemoglobin.

Nutritionists are quick to point out that while Burger King’s new offering is meatless and plant-based, it is not a health food. The vegetarian Whopper has the same amount of fat as a traditional beef patty, and nearly as much saturated fat.

The original Whopper has 12 grams of saturated fat; the Impossible Whopper has 11 grams. The Impossible Whopper also has nearly as many calories as the original – 630 calories for the plant-based burger versus 660 calories for the beef burger.

The Impossible Whopper is significantly saltier than the meat version, with 1,240 milligrams of salt versus the beef version, with 980 milligrams of sodium. Currently, the plant-based burger is only available in the St Louis, Missouri, area. The Impossible Whopper comes with mayonnaise, so it is not considered vegan.

“I wouldn’t call it a health food, although I feel like it’s more gray than that,” said Sharon Palmer, a registered dietician and author with a focus on plant-based foods.

“There have been highly processed veggie burgers around for a long time, and people who have been eating these within the context of an overall healthy diet are still having health benefits compared to a typical western diet.”