I have not had any of McD/BK/Wendys/TacoBell/Other in over 25 years, not even once. But I do go to any of the local tacquerias about once or twice/month, and even a Chipotle bowl every few months. Does that mean I am one of the 8/10 that eat fast food?
My point is, the traditional definition of "fast food" that is associated with one of the very large multinational corporations has been expanded or revised over the years. There are many healthy options, at least here in Nor-Cal, where one can eat healthy in a fast-food format (e.g., SushiRitto, Asian Box, Fresh Roll, etc.).