The great thing about a modified fast of three days is that it’s accessible for a lot of people for whom fasting generally isn’t a great option, including older adults.  Water fasting isn’t recommended during pregnancy or the first few months of exclusive breastfeeding, or for people who have an eating disorder, hypertension, diabetes, kidney disease, or heart disease.  People in cachexia (muscle wasting) from stage IV cancer should consult their physician, but even modified fasting is usually contra-indicated in this situation. When in doubt, talk with your trusted functional medicine doctor about whether a modified fast is right for you.