Design and validation of a fasting mimicking diet

INTERVENTION: Participants are randomised by central computer in permuted blocks (size unknown to all involved) in a 1:1 ratio to either the 12/12 (or 24/24 if 12 hours would be not sufficient) caloric restriction (CR) regime followed by feeding or feeding followed by CR. All outcome assessors will be blinded for treatment allocation. Nutritional targets will be achieved by EN±PN, as appropriate with a full feeding target of 20‐25 kcal/kg ideal body weight, a dosage defined by age (< or > 60 years) and gender. During fasting intervals, no nutrition will be administered, unless spontaneous hypoglycemia occurs. The intervention is thus to infuse enteral and/or parenteral nutrition as required to achieve nutritional target during a 12 hours (or in faze 2: 24 hours) interval on ICU day 8. This is followed by a 12 hours or 24 hours fasting. The sequence of this metabolic cross over experiment is determined by randomization. Plasma bilirubin, creatinine, BUN and glucose values and insulin requirements will be collected at study start, after the fasting window and after full feeding. Blood samples for evaluation of other changes in metabolism and cellular biology will be drawn likewise before and after the feeding and fasting interval. CONDITION: Prolonged critical illness ; Signs and Symptoms ; Prolonged critical illness PRIMARY OUTCOME: 1. Plasma bilirubin is measured by colorimetric assay in the Laboratory of Intensive Care Medicine at baseline and after the first and second intervention time window (12 hours or 24 hours according to the study phase); 2. Insulin requirements (total dose delivered over intervention time interval, this is the last 12 hours or 24 hours according to the study phase) are measured by reviewing the ICU‐PDMS (Patient Data Management System [Metavision]) at baseline and after the first and the second intervention time window (this is after 12 hours and 24 hours in the first phase and eventually after 24 hours and 48 hours in the second phase of the study) SECONDARY OUTCOME: 1. Mortality is measured using data from the National Registry via Hospital Clinical Work Station (KWS) at 90 days; 2. New ICU‐Morbidity occurring in the first week after randomization is assessed by reviewing the ICU‐PDMS (Patient Data Management System [Metavision]) at baseline and 7 days INCLUSION CRITERIA: 1. Adult ICU‐patients 2. Unable to eat by mouth 3. Expected on day 7 to stay 3 more days in ICU