I kind of inadvertently did some fasted exercise this summer. Too hot to hit the trails later, so was getting up between 4 and 5 and hitting the trails for an hour or two without breakfast- along with a nights sleep, was fasting for ~ 12-14 hours.
I'm a big fan of Uphill Athlete and they have a lot of data supporting fasted exercise, not for weight loss but to get better fat utilization during long aerobic endeavors. They stress the fast should be in the 10+hour range, the exercise should be low zone (2-3) workouts and not for much more than two hours- that's exactly what I was doing, but like I said really inadvertently
