Protein Dosing Strategies in Critically Ill Patients: Comparing Actual Body Weight and Fat-Free Mass Approaches in an Observational Cohort Study

LEan Body Mass Development in CriTically Ill Patients, Obtained by bioelectRical impEdance Analysis: a Combined Retrospective and Prospective Observational Cohort Study

This study investigates how different methods of calculating protein intake affect recovery and muscle preservation in critically ill patients in the Intensive Care Unit (ICU). Protein is essential for maintaining muscle strength, supporting healing, and improving recovery during critical illness.

At Hospital Gelderse Vallei, patients admitted to the ICU received protein based on actual body weight until 2023; more recently, protein prescriptions have been based on fat-free mass. Bioelectrical impedance analysis (BIA) has been part of standard clinical practice in the ICU since April 2020, meaning that all patients admitted since then have been screened for inclusion in the study.

This design allows for comparison between two groups: one group receiving protein based on actual body weight according to current clinical guidelines (1.5 g/kg body weight), and another group whose protein intake is calculated based on lean body mass (LBM) measured by BIA. BIA measurements are repeated during the ICU stay to monitor changes in body composition.

A total of 310 patients admitted to the ICU between the start of BIA implementation in April 2020 and the transition to fat-free mass-based dosing in 2023 were identified. To allow for balanced comparison, an equal number of 310 patients from the subsequent period, in which protein dosing was based on fat-free mass, were included in the study.

The study compares these two groups to determine whether calculating protein requirements based on lean body mass leads to better clinical outcomes-such as improved recovery (lower mortality and shorter hospital stay), preservation of muscle mass, and lower UCR-than the traditional method based on actual body weight. The data analysis plan was established prior to completion of patient inclusion and database lock.

Study Overview

• Status: Recruiting
• Conditions: Critical Illness

Detailed Description

Patients were enrolled through an opt-out procedure using an information leaflet included in the admission folder. The acquisition of informed consent from patients admitted between April 2020 and July 2023 was deemed neither necessary nor feasible, as the study relies on an anonymized database and no additional measurements are performed. Therefore, the internal committee for research evaluation approved the waiver of informed consent for these patients.

• Study Type: Observational
• Enrollment (Estimated): 620

Contacts and Locations

• Study Contact: Name: M. C. Paulus, MD; Phone Number: 0318434868; Email: mpaulus@zgv.nl

Study Locations

• Netherlands
  • Ede, Netherlands, 6716RP
    • Recruiting
    • Gelderse Vallei Hospital
    • Contact: M. C. Paulus, MD; Phone Number: +31318434868; Email: mpaulus@zgv.nl

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Probability Sample

Study Population

Critically ill adult patients

Description

Inclusion Criteria:

• ≥18 years old
• a BIA measurement available within 48 hours after ICU admission
• at least one follow-up BIA measurement during ICU stay.

Exclusion Criteria:

• transfer from another ICU resulting in the first BIA measurement >48 hours after admission to GVH
• a previous ICU admission within 2 weeks before the current admission.

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort
ABW fed; This group received proteins based on 1.5 grams per kilogram actual body weight
FFM fed; This group received proteins based on 1.85 grams per kilogram fat free mass (BIA determined)

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Mortality	Short (ICU and 30-day mortality) and long-term mortality (90 days)	Mortality, defined as death from any cause, from ICU admission until 90 days post-admission

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
ICU and hospital length of stay	Duration of ICU and hospital length of stay in days	From ICU admission until the date of ICU discharge or the documented date of death from any cause, whichever comes first, assessed up to 52 weeks after ICU admission
Duration of invasive mechanical ventilation (IMV)	Duration of invasive mechanical ventilation in days	Number of days on invasive mechanical ventilation (IMV), defined as the total number of days with IMV from initiation until ICU discharge, assessed up to 52 weeks after ICU admission
Urea-creatinine ratio during ICU stay	Differences in urea-to-creatinine-ratio between both groups during ICU stay	All UCR measurements taken during the ICU stay, from ICU admission to ICU discharge, with each measurement recorded daily and specified by the day relative to ICU admission, up to a maximum of 52 weeks
Changes in BIA parameters over time (in kg)	Changes in BIA (bioelectric impedance analysis) parameters, including fat free mass, sketetal mass and fat mass (all in kg)	All BIA measurements during the ICU stay, including dry fat-free mass, skeletal muscle mass and fat mass, recorded daily from ICU admission to ICU discharge, up to 52 weeks.
Changes in BIA water parameters over time (in L)	Changes in BIA water (bioelectric impedance analysis) parameters in liters	All BIA measurements during the ICU stay, such as intracellular water, extracellular water, and total body water, recorded daily from ICU admission to ICU discharge, up to 52 weeks
Changes in BIA phase angle	Changes in BIA phase angle	All BIA measurements during the ICU stay, such as phase angle, recorded daily from ICU admission to ICU discharge, up to 52 weeks

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Protein intake during ICU stay	Daily and cumulative (during the first 14 days) protein intake during ICU stay	Daily intake for the first 14 days since ICU admission, or all days on the ICU if this is less than 14 days
Energy intake during ICU stay	Daily and cumulative (during the first 14 days) energy intake during ICU stay	Daily energy intake for the first 14 days since ICU admission, per day, of all days of ICU stay if ICU stay is shorter than 14 days
Changes in Resting Energy Expenditure (REE) measured with indirect calorimetry	Changes in Resting Energy Expenditure (REE)	All REE measurements during the ICU stay, recorded daily from ICU admission to ICU discharge, up to 52 weeks

Collaborators and Investigators

• Sponsor: Gelderse Vallei Hospital

Study record dates

Study Major Dates

• Study Start (Actual): April 1, 2020
• Primary Completion (Estimated): February 1, 2026
• Study Completion (Estimated): February 1, 2026

Study Registration Dates

• First Submitted: December 5, 2025
• First Submitted That Met QC Criteria: December 17, 2025
• First Posted (Actual): December 31, 2025

Study Record Updates

• Last Update Posted (Actual): December 31, 2025
• Last Update Submitted That Met QC Criteria: December 17, 2025
• Last Verified: October 1, 2025

More Information

Terms related to this study

• Keywords: fat free mass; critical illness; BIA; lean body mass; proteins
• Additional Relevant MeSH Terms: Pathologic Processes; Disease Attributes; Pathological Conditions, Signs and Symptoms; Critical Illness
• Other Study ID Numbers: 2403-017

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No