I don't ride on intermittent fasting days, or I eat a couple of hours before I do ride. I know from years of experience I'll bonk hard if I try to ride without eating. If I've gone 12-20 hours without eating and still want to ride or exercise, I'll have my usual pre-ride meal: oatmeal, banana and yogurt, with coffee. Works reliably for me.
But I doubt I have enough stored fat to test any theory on diet and exercise. It might work for folks with enough stored fat, no history of blood sugar problems, and other metabolic variables that make it work for them. Some anecdotes claim women are better suited to that sort of approach. I just know it doesn't work for me.
I do have a few pounds of fat around the middle and I'm so close to being optimally lean that I'm tempted to give it a try at paring down. Just for the challenge, no particular goal. But I'd need a much more methodical approach, and I'd need to decide whether I'm willing to sacrifice my few vices: a few beers a week; creamer in coffee, muffins with breakfast a few times a month (less than I used to eat), an occasional cookie or bit of chocolate hours away from any workout where those sugars and carbs won't be burned up.
So for now I'm depending on 2-3 hard rides a week at or near maximum sustainable effort, including one a week with HIIT. Seems to be working, which kinda reduces my motivation to sacrifice any more than I already have. I'd need to be persuaded that losing 2-5 lbs of fat would result in a significant improvement in my bike riding power and speed. But it won't. My primary obstacles are unrelated to weight -- mostly respiratory and a couple other pesky issues. Losing a couple or few pounds won't matter.