From TFA (http://www.cell.com/cell-metabolism/fulltext/S1550-4131(15)0...): The development of the human diet took into account feasibility (e.g., high adherence to the dietary protocol) and therefore was designed to last 5 days every month and to provide between 34% and 54% of the normal caloric intake with a composition of at least 9%–10% proteins, 34%–47% carbohydrates, and 44%–56% fat.