Who wants to bet that 75% of the replies here will have nothing to do with the topic and just say "OHH NOS cuz fast fud is bad 4 u! :mew2:"?
Never less than once a month, never more than once a week. I'm very partial to the McChicken sandwich, and I might have two of those on the weekend, and seeing as the only restaurants in my town are McDonald's, Burger King, Long John Silver's, Pizza Hut, Subway, and Domino's, I don't have much of a choice. Not counting the times about once a month that I can go to the city for some Wendy's or Taco Bell, I might have McDonald's 30 or so times a year, Pizza Hut six times, and Subway twice. So, come to think of it, a better option for me might be fortnightly.