Resumed aikido here recently, 2x a week.
I used to fast on the day after training but now that training has picked up (yesterday was over 2hrs and intense, my whole body feels like I've been beaten with a stick) I don't think it's wise to fast when I should be recovering, right? I will switch to the 2nd day after (training is 2 consecutive days -- kinda rough).
If I had to, I could fast on a training day -- never hungry on the mat and better to NOT have a full stomach with all those falls and rolls. haha I might adapt the 5:2 though and maybe do 30-40% of calories those days (some of the studies MM used showed benefit at 40%) or even break the 36-hr fast (if you go 7pm-7am) into 2 18hr fasts (or just do 24hr fasts) so that you can eat before or after a practice. I've "split my fast in two" when I was fasting an a migraine (I already had) got too severe and I had to stop fasting. I "finished up" my fast the next day.
I am curious how other people handle recovery from intense workouts, though.