Something else to consider is that working out while fasted will help you enter ketosis sooner, where you start burning fat instead of the carbs you consumed during your previous eating window . This will be especially impactful if you are doing longer fasts (18hr+).
Anecdotally, I have been doing 20:4 and working out halfway through my fast and my weight has dropped very quickly (4.5lbs/wk). Just make sure you stay VERY well hydrated and stop immediately if you feel dizzy or lightheaded. It hasn’t ever happened to me, but listen to your body!