Plain English Summary
Background and study aims
Critical illness is a state in which patients depend on drugs or machines to support or replace organ function to keep them alive and allow them to heal. Such patients are admitted to intensive care units (ICU) to receive care. Critically ill patients are at risk of losing muscle power due to due to the natural breakdown of tissue from inactivity. Short term fasting may be beneficial in the recovery of disease. Even in ICU, withholding intravenous nutrition (nutrition delivered through a drip) for one week, surprisingly, avoids complications and allows severely ill patients to recover faster and go home earlier. This study is aiming to see if these beneficial effects can be broadened beyond the first week of critical illness. The aim of this study is to design a new fasting mimicking diet in ICU (ICU-FM) based on cyclic feeding interruptions and look at its effects.
Who can participate?
Adult patients in ICU who are unable to eat by mouth.
What does the study involve?
Participants are randomly allocated to undergo 12 hours of receiving nutrition through a drip or straight into the gut followed by 12 hours of fasting, or 12 hours of fasting followed by 12 hours of receiving nutrition through a drip or straight into the gut. If the 12 hour time period is judged to be insufficient, then the process is repeated using 24 hour time periods. At the start of the study and then after 12 or 24 hours (depending on the time period used), participants have samples of blood collected to assess their health. In addition, participants have their medical records reviewed after 7 and 90 days to assess survival rates.
What are the possible benefits and risks of participating?
There are no direct benefits or risks involved with participating.
Where is the study run from?
UZ Leuven (Belgium)
When is the study starting and how long is it expected to run for?
June 2016 to October 2017
Who is funding the study?
1. KU Leuven (Belgium)
2. Flanders Government FWO (Belgium)
Who is the main contact?
Dr Michael P. Casaer
ICU-FM: Implementation into the intensive care unit (ICU) of the beneficial effects of fasting (mimicking diets) (FM)
Twelve hours of nutrient restriction are sufficient to provoke a metabolic fasting response in critically ill patients, as reflected by increased plasma bilirubin and decreased insulin requirements.
Commissie Medische Ethiek UZ KU Leuven , 27/07/2016, ref: B322201629914
Pilot randomised cross-over study
Primary study design
Secondary study design
Randomised cross over trial
Patient information sheet
Not available in web format, please use the contact details below to request a patient information sheet. Available in Dutch and French.
Prolonged critical illness
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.
Primary outcome measure
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 measures
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
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
1. Adult ICU-patients
2. Unable to eat by mouth
3. Expected on day 7 to stay 3 more days in ICU
Target number of participants
70 patients (and possibly another 70 patients fasted for 24 hours if 12 hours is not sufficient)
Total final enrolment
Participant exclusion criteria
1. Patients with severe jaundice
2. Bilirubin > 5mg/dL, pregnant
3. Lactating patients
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Clincial Department of Intensive Care Medicine Herestraat 49
Katholieke Universiteit Leuven
Funding Body Type
private sector organisation
Funding Body Subtype
Universities (academic only)
Flanders Government FWO
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
The results of this STEP-I pilot study will primarily serve the adequate design of ICU-FM-II, a clinical study exposing a larger group of patients to a longer time window of fasting mimicking versus normocaloric feeding. Publication of the results of this second study is planned in a high impact journal around 2019.
IPD Sharing plan:
The participant level data of this step I pilot metabolic cross over clinical experiment will not be publicly available. This would be a potential source of erroneous findings due to inadequate interpretation of the study design. The data will be stored in the research database of the Clinical Department and Laboratory of Intensive Care Medicine and request for post-hoc analyses with a clearly defined research question and methodology can be sent to the investigators. This approach to avoid misinterpretation of complex data and databases has been proposed in a recent summit on data-sharing organized by the NEJM in April 2017.
Intention to publish date
Participant level data
Not expected to be available
Basic results (scientific)
2020 results in https://pubmed.ncbi.nlm.nih.gov/32448392/ (added 26/05/2020)