Satisfries $$$$

While French fries are a staple of the fast-food burger business, they have long been vilified by nutrition experts as little more than vehicles for adding fat, salt and calories to diets.

Now Burger King has come up with a fry that it says delivers about 40 percent less fat and 30 percent fewer calories than the fries sold by its archenemy McDonalds . Burger King says that 70 grams of its new fries, named Satisfries, has 150 calories, while the same amount of McDonald's fries has 226 calories.

"You live in Manhattan and might be having a kale smoothie on your way to work this morning," said Eric Hirschhorn, chief marketing officer for Burger King, the nation's No. 3 hamburger chain after McDonald's and Wendy's. "But a lot of people don't even know what kale is, and if they do, they don't want to eat it. You have to give people what they want."

Burger King, which has struggled as a series of owners traded it like a baseball card, was late to try to improve the nutritional quality of its food.

But under its newest owner, the private equity group 3G Capital, the chain has invested time and money in retooling its menu over the last two years, adding choices like cranberry apple salads and mango smoothies and taking one of two slices of cheese off its burgers in the biggest changes to its menu since opening in 1954.

"Behavior doesn't change as quick as attitudes," Mr. Hirschhorn said. "It's easy to put things on a menu and check off the box, but the reality is that nobody buys them."