Not necessarily junk food but the chem's that are in them. I've sworn off HFCS and Phosphoric acid. High fructose corn syrup is in just about everything and an article that I read recently re: Phosphoric acid in Coca Cola and Pepsi, leads me to believe that is what makes me feel stiff in the joints in the morning. I've been off Coca Cola and Pepsi for 6 months now and I can honestly say the stiffness in the joints is gone.