Three days! That is the maximum period that you can live without food. You can live for one day without water and three days without food. But of course this also depends on where you are. If you are stranded in the desert and you lose a lot of energy then three days might be too much of an estimate. Why do you want to know this anyway? Are you planning to starve yourself? My son went through one of these phases and decided to stop eating completely. In the end we had to admit him into the hospital for malnutrition.