Burger King Worldwide, known for its "Whopper" hamburgers, is introducing lower-fat French fries, as consumer groups in the US increase pressure on the food industry to offer healthier alternatives.

The hamburger chain said on its website late on Monday it had come up with fries containing 40 percent less fat and 30 percent fewer calories than those sold by its arch rival McDonald's Corp.

McDonald's could not immediately be reached for comment by Reuters outside regular U.S. business hours.

More than one-third of Americans are obese and about 10 percent of the nation's healthcare bill is tied to obesity- related diseases, such as Type 2 diabetes, heart disease and hypertension, according to the Organization for Economic Co-operation and Development.

As a result, health and parents' groups are lobbying to try to bring about change in the U.S. food and beverage industries.

Last week, First Lady Michelle Obama asked television and food company executives at a White House gathering to sell youngsters on healthy food with the pitch: "If anyone can make our kids eat their vegetables, it's all of you."

In 2011, the Federal Trade Commission failed to get food and beverage makers to agree to voluntary guidelines on marketing to children. Since then, there have been various initiatives by individual companies or business coalitions to reduce calories in their products or set a code of conduct on marketing. – Reuters