Last Thursday was the first day of my water fast, right smack dab in the middle of my period.. toward the tail end of it now. I havent had any problems, cramps have been minimal. I can't tell if I've been more fatigued from water fasting (and over doing it) or if it's just because it's coupled with my period. who knows. like the the other poster said, you may have more intense cravings and "hunger" pains, it just depends on you. mentally, i was totally in the zone and i just KNEW i was ready to start another water fast. i havent felt any sort of hunger since starting. i'm going through to the end of the month (15 day water fast, then 3 on vegetable juices, & 3 incorporating some fruit juice). good luck!