Energy Expenditure

EE: Introduction (2014)

Guideline Overview

Guideline Title

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.

References

Matarese LE. Indirect calorimetry: technical aspects. Journal of the American Dietetic Association. 97.10 (Oct. 1997): pS154.

Feurer I and Mullen JL. Bedside measurement of resting energy expenditure and respiratory quotient via indirect calorimetry. Nutrition in Clinical Practice. 1986: 1: 43.
 
Rationale for Focusing on Measurement of Resting Metabolic Rate  

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.
Share of the Total Energy Expenditure. In healthy and non-critically ill individuals, the energy expended in a basal state typically accounts for 60-70% of TEE, the TEF typically accounts for 7-13% of TEE, and physical activity (the most variable of the components), typically accounts for 15-20% of TEE [Erdman et al (Eds.), 2012]. 

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.

References
 
Erdman, J., Macdonald, I. and Zeisel, S. (Eds.). (2012). Present Knowledge in Nutrition. (10th ed.). Chapter 5. Hoboken NJ: Wiley-Blackwell Publishers.

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).  

Reference:
 
Food and Nutrition Board. Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids,  cholesterol, protein, and amino acids (macronutrients). National Academy Press; Washington (DC): 2005.  
 
Medical Nutrition Therapy in Healthy and Non-Critically Ill Populations
 
Scientific evidence supports the importance of the Registered Dietitian Nutritionist (RDN) as a member of the interdisciplinary team caring for healthy and non-critically ill individuals. In many settings, it is the RDN who carries out indirect calorimetry measurements as an important component of the nutrition care process.

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.
 
Guideline Development and Contributors

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:

Topics include:
  • 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)
The number of supporting documents for these topics is below:
  • Recommendations: 19
  • Conclusion Statements: 19
  • Evidence Summaries: 13
  • Article Worksheets: 44
Revision

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
  • Guideline Methods
  • Implementation of the Guideline
  • Benefits and Harms of Implementing the Recommendations
Clinical judgment is needed to determine when the RMR will be a critical element of the nutrition care plan and likely to significantly impact important patient/client outcomes. Regardless of the method to determine RMR (i.e., estimated or measured), careful clinical judgment is essential to evaluate the RMR value and its application in an individual’s nutrition care and outcomes.