I have been on intermittent fasting for over a year. Usually no food during the day. I am an avid runner so I can attest that your running performance is not too impacted, especially on long flat runs, hills another story. Shorter, harder runs you do get a somewhat immediate hit. I have run 10 miles easy while fasting, anything over you start to feel it. I have also ran my fastest recorded mile while fasting, just under 6 mins/mile. Of course as you lose weight you get faster, that’s also a benefit of intermittent fasting.