No, you have been propagandized about fasting. The medical community knows very little about fasting and doesn't want to learn more--not beneficial to their bank account to have you get well without them billing you. (Same reason the medical community and the pharmaceutical industry do not want you exploring chiropractic, acupuncture, massage, naturopathic medicine, Aryuvedic, yoga, homeopathy, etc., etc,.)
During a fast you can continue working hard and living your life as normal. In fact, you will get stronger during the fast because you are eliminating toxins that are contributing to your ailments and early tiredness. I usually do juice fasts because water fasts are just too difficult for me. You are already fasting each night until you break your fast with a breakfast (break-fast). There is a lot of great information out there about fasting--also a lot of disinformation, too. But. the proof is in the pudding. Try it, you'll like it.