none have been shown
fructoise is just another naturally occurring sugar, and the body uses it just like glucose.
from mayo clinic:
"... recent research — some of which is supported by the beverage industry — suggests that high-fructose corn syrup isn't intrinsically less healthy than other sweeteners, nor is it the root cause of obesity. "
it's not the fructose that's the problem - it's the fact that people eat too much SUGAR period.