The Science of Fasting

I've been doing 22 hours fasts a couple of times a week for the past two months. Combined with hitting the gym three times a week for about 6 hours of relatively intense workouts, I have lost over 10 lbs of weight and put on some muscle (so I'm probably 12-15 lbs down on fat). It's been working well and the fasting hasn't impacted my workouts at all. I usually will fast from breakfast the day before my scheduled workout until breakfast the morning of.

So, this week I decided to go for a 36 hour fast. Worked out on Monday and had all of my meals. I hit the start button at 7 PM on Monday night and fasted until 7 AM this morning. Honestly it wasn't that difficult. I don't seem to experience intense hunger feelings. Mainly it's a constant desire for food that is probably more mental than physical. So, this morning I ate a little more than my usual breakfast, but nothing crazy. Made sure I also hydrated. But today my workout was definitely impacted by the fast. I usually start with about 25 minutes of relatively strenuous cardio. I had to call it off around the half way mark because my legs started cramping. Haven't experienced that to this point with the 23 hour fasts. I also didn't feel quite as energetic when lifting and have had a few more slight cramps in my arms this afternoon. I am going to try a 36 hour fast at least one more time to make sure this isn't all a coincidence, but if it happens again I'll be backing off to the shorter ones.

Has anyone else ever experienced this? If so, did you figure out a remedy? Thanks!