OAK BROOK, Illinois -- McDonald's Corp. said Tuesday it would cut the amount of unhealthy fats in its trademark fries and other fried foods by almost half, in an effort to improve the health value of its food.

Beginning in October, the fast food chain will switch to an "improved cooking oil," with a higher content of polyunsaturated fats and a lower amount of the artery-clogging trans-fatty acids and saturated acids.

The move will cut fatty acids in McDonald's fries by 48 percent, reduce saturated fat by 16 percent and increase polyunsaturated fat by 167 percent, delivering "health dividends" for the customer, the chain said.

"It's a win-win for our customers because they are getting the same great french fry taste along with an even healthier nutrition profile," said Mike Roberts, President of McDonald's U.S.A.

Trans-fatty acids and saturated acids are associated with a higher level of low density lipoprotein (or LDL) cholesterol -- a risk factor for heart attack and stroke.

Cardiovascular disease is the number one killer of Americans.

"It may seem like a small change, but it has huge implications because so many Americans go to this type of fast-food restaurant," said Gregory Miller, President of the American College of Nutrition.

The chain has 13,000 outlets in the United States and 30,000 worldwide, serving 46 million people each day.

Robert Eckel, the American Heart Association's (AHA) point man on the subject, called it a "modest step in the right direction," and said he hoped other fast food chains would step up and provide healthier fast-food choices also.

But he also pointed out that the new cooking oil will not reduce the fat content or calories in a serving of McDonalds fries, chicken mcnuggets, filet-o-fish, hash browns or crispy chicken sandwich.

"The public needs to remain alert to the portion size and calorie content of fast-foods," said Eckel, who heads up the association's nutrition council.

With a serving of fries accounting for anywhere from 210 to 610 calories (small/super-size order), and obesity reaching epidemic levels in the United States, all the experts warned that consumers should include fast food only as part of a balanced diet.

"This won't make McDonald's french fries a health food," said Margo Wootan, Spokeswoman for the Center for Science in the Public Interest, noting that a large order will still have 540 calories and almost a third of a day's worth of artery-clogging fat.

One in four Americans is obese according to recent research, and obesity is also a major risk factor for coronary heart disease, contributing to elevated blood pressure and cholesterol levels, according to the AHA.

Still, even the CPSI commended McDonald's for its actions Tuesday, something which it has been calling for since 1993.

As to timing, mcdonald's said it based its decision on a critical mass of scientific evidence showing the value of polyunsaturated fats.