As the United States continues struggles with an obesity rate of every 1 in 3 adults, a recent study says major fast food chains have "barely improved nutritional quality of menus in 14 years", further spurring the obesity epidemic.

According to the study "Nutritional Quality of Menu Offerings at Eight U.S. Fast-Food Chains: 14-Year Trends" published in the American Journal of Preventive Medicine, over 25 percent of American adults chow down on fast food two or more times a week. These meals are packed with huge amounts of fat, sugar, and salt, contributing to America's poor diets and increased risk of diet-related chronic diseases, like heart disease and diabetes.

"Despite qualitative evidence that the fast-food industry is making improvements to the nutritional quality of at least some of their menu items, a quantitative evaluation of trends in the nutritional quality of fast food available in the marketplace was lacking," says lead investigator Mary Hearst, PhD, MPH, Associate Professor of Public Health at St. Catherine University in St. Paul, Minnesota.

"This is the first study to quantitatively evaluate whether fast-food restaurant chains have improved the nutritional quality of their U.S. menu offerings over a period of time during which they have been encouraged to do so by governmental and nongovernmental agencies."

Researchers analyzed the following fastfood chains between 1997 and 2010:

  • McDonald's
  • Burger King
  • Wendy's
  • Taco Bell
  • Kentucky Fried Chicken (KFC)
  • Arby's
  • Jack in the Box
  • Dairy Queen

To evaluate nutritional quality, researchers relied on the Healthy Eating Index (HEI)-2005, a metric developed by the U.S. Department of Agriculture and used for quantifying nutritional quality. The team expected index scores would fall below the score for the American food supply - 60 points of 100 - due to high fat and sugar and low fruit and vegetable content. It also expected to find an increase in HEI-2005 scores among these restaurants over the 14-year period.

Scores improved for meat, saturated fat, and calories from solid fats and added sugars. Scores worsened for milk/dairy and sodium. They did not change for fruit, whole fruit, total vegetables, dark green and orange vegetables, legumes, total grains, whole grains, and oils. The study found that KFC did best in increasing vegetables and total grains and decreasing saturated fats, solid fats, and added sugars.