[beagle3]

You actually should exercise while fasting. When fasting, t he body gets rid of fat, and any muscles that are not essential. Which makes a lot of sense - maintaining muscle costs both protein and energy, even if they aren’t used much.

I did not try to run quickly while fasting, but I did keep doing my 5km 3 times per week, and the gym. Anaerobic was hard and quickly tiring, but aerobic exercise wasn’t really any harder.

A friend did point out that my movement was “more economical” in general - I hardly lifted my feet while running or walking, and a few other things. But I didn’t feel more tired or more strained, except for unaerobics.