Research has indicated that fast food chains are slowly moving towards offering healthier food for consumers.

The results indicated that between 1997 and 2008 McDonald's, Burger King, and Wendy's reduced the trans and saturated fatty acid levels in French fries served at their outlets.
"I'm also pleased to see that they haven't raised levels of saturated fats to replace trans fats," said Lisa Harnack, PhD, an associate professor of epidemiology in the School of Public Health and director of the Nutrition Coordinating Center.
The other two chains have decreased the levels of trans fats since 2008. Trans fats have been implicated in heart disease risk in several studies.
Source-Medindia