I have some friends in their 70's who are very spiritual and do a lot of counseling and they fast every week from Wednesday lunch to Friday lunch - they do it for spiritual reasons and set aside special longer times of prayer and meditation every Thursday (in addition to their daily prayer and devotional practices) and they seem very strong and healthy (as well as being very level-headed and sane) - I always admired them and wanted to incorporate something similar into my regular life. I think they also set aside longer periods of time for fasting during Lent and Advent. To me it seems like a very balanced way to add the benefits of fasting into your everyday life - whether it is for health benefits or spiritual reasons, I say - go for it!