EE: Introduction (2014)
Energy Expenditure (2014) Measuring RMR in the Healthy and Non-Critically Ill Evidence-Based Nutrition Practice Guideline
Guideline Narrative Overview
An accurate measurement of resting metabolic rate (RMR) with indirect calorimetry is important for both clinicians and researchers. The purpose of this guideline is to help the practitioner identify the conditions under which she/he can perform an indirect calorimetry measurement to accurately measure RMR in healthy and non-critically ill individuals and properly interpret the results. The majority of studies used in the development of this guideline were conducted on healthy adults; however, a few of the recommendations included studies conducted on healthy children or adults with chronic disease, but who were not critically ill.
The project set out to answer or update 12 questions related to the accurate measurement of RMR in healthy and non-critically ill individuals. General inclusion/exclusion (I/E) criteria were established a priori for the screening of articles. Later, more specific and strict I/E criteria were established based on evidence analysis of each question. For example, analysis of the data for fasting and the resting periods prior to a measurement suggested that individuals should fast for a minimum of seven hours, or overnight; and the rest period prior to initiating data collection should be a minimum of 20 minutes (or 15 minutes of rest and five minutes of discarded data). Therefore, studies that did not meet these criteria or did not describe the resting and fasting periods were excluded for all questions. Studies that reported sleeping metabolic rate (SMR) rather than RMR were also excluded. Studies that measured basal metabolic rate (BMR) were included because evidence suggests that study designs which met all the criteria identified in this RMR guideline were equivalent to a BMR (Matarese, 1992; Feurer and Mullen, 1986). When the phrase “more research is needed” appears in a recommendation, it implies that research applying all the protocol standards identified in this guideline should be followed to more clearly answer the question.
Feurer I and Mullen JL. Bedside measurement of resting energy expenditure and respiratory quotient via indirect calorimetry. Nutrition in Clinical Practice. 1986: 1: 43.
The purpose of this guideline is to provide instruction on the appropriate method of achieving resting conditions and measuring RMR in healthy and non-critically ill individuals. Resting metabolic rate is only one component of total energy expenditure (TEE) [i.e., total metabolic rate (TMR)]. The other components include the thermic effect of feeding (TEF) and the energy expended during movement. These components must be estimated and added to the measured RMR to determine the TEE. In this guideline, we focus on RMR for four reasons:
- 1) RMR is the largest component of TEE;
- 2) RMR is the most reproducible of the components of TEE;
- 3) RMR is comparable to a reference standard; and
- 4) RMR is the most feasible component of TEE to measure.
Reproducible. Resting metabolic rate is the most reproducible component of TEE. The state of rest is clearly defined, with specific conditions of environment and subject preparation, if followed, produce a near minimum level of metabolic rate. This state can then be reproduced over time within an individual and across populations. Total energy expenditure is more difficult to reproduce because the environment and personal attributes, such as diet, movement and sedation level, are highly variable.
Comparison to a Reference Standard. From a nutrition diagnosis perspective, measurement of the RMR allows the RDN to diagnose alterations in energy expenditure as compared to a healthy reference standard. For example, a PES statement may be written as: Increased nutrient needs (energy) related to inflammatory response as evidenced by measured RMR 30% above healthy RMR calculated by the Mifflin-St. Jeor equation. There are no reference standards for activity level or TEF because of high variability in these components of TEE.
Feasibility. If conditions are controlled as outlined in this guideline, a measurement of RMR can be accomplished within 30 minutes. However, measurement of TEE may require considerably more time, and this time requirement severely limits the number of patients that can be measured (Zijlstra et al, 2007). RMR is therefore the more feasible of the two parameters to measure.
Zijlstra N, ten Dam SM, Hulshof PJ, Ram C, Hiemstra G, de Roos NM. 24-hour indirect calorimetry in mechanically ventilated critically ill patients. Nutr Clin Pract. 2007; 22: 250-255.
Extrapolation from Resting Metabolic Rate to Total Energy Expenditure
Conversion of the measured RMR to an estimation of TEE (which includes TEF and physical activity as well), is an important step in determining the energy goal for an individual, but there are few data to guide the process. Clinical judgment must be applied to the multiplication factors used to convert RMR to TEE. Alternatively, the Dietary Reference Intake equations (which are based on data from doubly labeled water) may be used to estimate TEE (Food and Nutrition Board, 2005).
The RDN plays an integral role on the interdisciplinary care team by determining the optimal nutrition prescription and developing the nutrition care plan for healthy and non-critically ill individuals. Based on the individuals’ health status and comorbidities, the RDN monitors and evaluates the effectiveness of the nutrition care plan in promoting the patient’s nutritional health and quality of life. The RDN adjusts the nutrition care plan as necessary to achieve desired outcomes.
This guideline outlines the most current information on measurement of RMR in the healthy and non-critically ill patient. The recommendations developed in this guideline were based upon a systematic review of the literature in multiple practice areas. To view the guideline development and review process, click here. A summary of the evidence analysis is below:
EE: Rest Period Duration
EE: Resting Activities
EE: Body Positions
EE: Gas Collection Devices
EE: Diurnal Variation (Time of Day)
EE: Room Conditions
EE: Fasting Requirements
EE: Caffeine and Stimulants
EE: Smoking and Nicotine
EE: Physical Activity
EE: Duration of Measurement (Steady State)
EE: Application of Respiratory Quotient (RQ)
Conclusion Statements: 19
Evidence Summaries: 13
Article Worksheets: 44
All Academy guidelines are revised every five years. The literature search will begin for each guideline topic three years after publication to identify new research that has been published since the previous search was completed. An expert work group will convene to determine the need for new and revised recommendations. See Revision under Guideline Development for more information. The updated guideline will be developed using the Academy of Nutrition and Dietetics Evidence Analysis Process (download a copy of the Academy Evidence Analysis Manual from the Methodology tab.)
New research may warrant a revision to a specific question or recommendation prior to the full project or guideline revision. Once identified, information is gathered and the EAL oversight committee will make a decision on the appropriate action.
Other Guideline Overview Material
For more details on the guideline components, select the topics below from the left navigation bar:
Scope of Guideline
Statement of Intent and Patient Preference
Implementation of the Guideline
Benefits and Harms of Implementing the Recommendations