Energy Expenditure

EE: Table 4. Evidence Analysis of IC, Factors for Consideration (2006)

Table 4: Considerations for Measurement in Indirect Calorimetry, Results from Evidence Analysis

Below are three tables that contain summaries from the evidence analysis of the important considerations for accurate indirect calorimetry measurement:

Considerations before measurement (Table 4.1)
Considerations during measurement (Table 4.2)
Considerations after measurement (Table 4.3)

Table 4.1: Considerations Before Measurement

Evidence Analysis Question	Conclusion Statement	Evidence Grade						Comments
Evidence Analysis Question	Conclusion Statement	Healthy Adults	Adult Patients	Institutionalized (transitional care, sub-acute)	Acute/ Trauma	Critically ill/Ventilated	Ethnic Populations	Comments
DIETARY INTAKE What are the effects (defined as peak magnitude and duration) of meals on resting metabolic rates in healthy non-obese adults and special adult populations (i.e., obese and older adults)?	Overall Conclusion Statement In most individuals, a fast of at least 5 hours prior to RMR measurement is preferred to reduce any impact of diet-induced thermogenesis, which is generally 7-9% of kcal consumed. However, if a 5-hour fast would create medical risks (e.g., diabetes), then a fast of at least 4 hours prior to a RMR measurement could be adequate to reduce any impact of diet induced thermogenesis if a small meal (i.e., 400 kcals or less) is consumed. If a very large meal (>900 kcal) is consumed within 5 hours of a RMR measurement, then a longer time (at least 6 hours) is recommended to reduce diet-induced thermogenesis to clinically insignificant levels (<100kcals/day).	II
CAFFEINE What is the acute effect of administration or changes in chemical use of caffeine and tea and herbal or dietary stimulants (including ephedra) on RMR? *Ephedra examined but banned from sale by FDA in April 2004.	Caffeine (acute): Available evidence does not permit conclusions on a dose-response effect of caffeine.	II
	Special Populations (Smokers): 6 to 10% increase in RMR above baseline over 30 to 180 minutes with concurrent use of caffeine and nicotine.	III
	Chronic Effect of Caffeine: Insignificant increase in RMR in men with a lower dose of caffeine. 8% in RMR in lean (mean BMI 24 +/- 1) Swiss females as compared to a 5% increase in age-matched obese individuals (mean BMI 28 +/- 0.9).	IV
	7-oxo-DHEA (e.g. 7-keto-Naturalean): No studies reporting short-term effects and no significant difference from baseline to 8 weeks in 7-oxo-DHEA vs. placebo.	IV
SMOKING Do administration or changes in chemical use of nicotine have an effect on RMR?	Acute Thermic Effect (males): RMR increased 4-9% in first 15-30 min. Elevated group mean RMR remained 2 hours post-nicotine exposure.	II						No data are available to indicate duration of chronic thermic effect of nicotine on RMR >8 and < 24 hours.
	Acute Thermic Effect (females): Increase in RMR of 7.5% at 60 min and 5.7% at 160 mins in one study with return to at or below baseline 30-100 min after nicotine.	IV
	Smoking cessation: RMR increase of 63.2 and 54.3 kcals/d two weeks after nicotine cessation in black and white individuals respectively.	IV
ALCOHOL Do administration or changes in chemical use of alcohol have an effect on RMR?	Acute thermic effects: 4-6% increase of RMR over 95 min following 20-23 gm of alcohol.	III
	Chronic thermic effects: RMR elevated 26% in middle-aged alcoholics but decreased to similar levels as non-alcoholic controls with 14 days of abstention.		III
	Alcohol ingestion with food: No effect is consistently supported.
PHYSICAL ACTIVITY What are the acute effects on RMR following physical activity in healthy adults and how long does it take for a post-exercise RMR measure to return to pre-exercise RMR?	Overall Conclusion Statement If individuals have performed low to moderate intensity exercise (i.e., walking, jogging, cycling, or weight lifting) for 30 minutes or less, a rest period of 2 hours is needed prior to RMR measurement. If aerobic or resistance exercise is performed at higher exercise intensities for longer durations, a rest period of 9 to 24 hours is probably acceptable, but 48 hours is preferable, prior to an RMR measurement to avoid measuring activity energy expenditure.	II III
MEDICATIONS What are the effects of medications on RMR?	Summary presented in Table 5.	II

Table 4.2: Considerations During Measurement

Evidence Analysis Question	Conclusion Statement	Evidence Grade						Comments
Evidence Analysis Question	Conclusion Statement	Healthy Adults	Adult Patients	Institutionalized (transitional care, sub-acute)	Acute/ Trauma	Critically ill/Ventilated	Ethnic Populations	Comments
NUMBER OF MEASURES How many times within a 24-hour period does the individual need to be measured?	One measurement is sufficient.	II		II
	One measurement is sufficient if steady state (SS) is achieved.					I
	In individuals unable to achieve SS or tolerate measurement conditions, two or more nonconsecutive single measurements may improve value.	II					II
TEST MEASUREMENT INTERVAL What is an acceptable energy measurement interval to reflect RMR?	10 minute measurement under steady state conditions (discarding the first 5 minutes of measurement).	II			I		IV
	20 minute measurement may be sufficient.			III			IV
	10 minute measurement (discarding first 5 minutes).					I	IV
STEADY STATE What is the acceptable coefficient of variation (CV) in oxygen consumption (vO₂) and carbon dioxide (VCO₂) production to reflect Steady State (SS) measure conditions and predict RMR?	10 minute protocol with 10% CV in vO₂ and VCO₂/minute using SS conditions (discarding first 5 minutes).	II
	5 minute measures at <5% CV or 30 minutes with <10%CV provides results comparable to longer duration measures of EE, and the 5-min and 30-min measures are highly correlated. Sedation has a significant positive impact on successfully achieving the SS criteria. For spontaneously breathing, critically ill patients, the 5-min SS protocol produces reliable RMR.					I
GAS COLLECTION DEVICES What is the energy measurement difference when using different types of gas collection devices, such as facemask, mouthpieces with nose clips, or canopy?	With no air leaks, comparable RMR measures can be achieved with facemask, mouthpieces with nose clips, or canopy. Conflicting data in one of five studies with mean RMR 7% higher in facemask and 9% higher for mouthpiece.	III
ROOM ENVIRONMENT What environmental characteristics controlled in research settings are necessary to apply in routine environmental settings to ensure an accurate RMR measure by IC?	Posture: In settings to obtain RMR measures in healthy or ill adult patients, a good recommendation is to ensure that the individual is physically comfortable with the measurement position during the test and repeated measures are in the same position. Posture (sitting vs. reclined): One study of plus research design quality, with a wide weight range, indicates a sitting RMR measure is 100 kcals higher/day than a supine RMR.	V	V
	Humidity: The question of whether increased humidity changes RMR measurements, and its results are inconclusive.	V
	Noise and lighting: Two narrative reviews representing expert opinion suggest that light and noise should be quiet for patients in critical care setting sand logically extend to other settings.					IV		No primary studies available in healthy adults (Grade V).
	Room Temperature: RMR is affected, to variable degrees in given individuals, by moderate cold exposure or ambient room temperatures outside of a comfortable zone (22-25°C) for healthy adults.	V
	Setting change (sleeping overnight as an inpatient vs. driving to an outpatient setting prior to measure): Low levels of physical activity related to daily living have minimal impact on RMR, provided that a suitable rest period follows the activity prior to measurement.	III
RESPIRATORY QUOTIENT Should RQ be used to detect measurement error in adults?	Overall Conclusion Statement Respiratory quotient (RQ) is the ratio of vC0₂and vO₂ and under proper conditions is a function of the mix of substrates being utilized for metabolism. An RQ of <0.7 or > 1.0, can be used to identify unusual metabolic or respiratory conditions, failure to adhere to the fasting requirement of the protocol, and/or operator or equipment error. A repeated measurement under more optimal conditions should be considered if and RQ value is outside the range of 0.70 to 1.0.	II
REST PERIOD LENGTHS What are the energy measurement differences if rest period lengths vary before measuring energy expenditure (EE) in healthy adults?	A minimum rest period length of 10-20 minutes is an adequate testing condition.	III
	Two narrative reviews are most frequently cited for the currently accepted 30-min. rest period.					IV
	An international study of negative research quality design indicates individual RMR differences (< 70 kcal/day) between measurements performed after awakening, being transported in a wheelchair and a 7-min. rest period compared to a RMR measure taken after light physical activity and a 20 min. rest.		V*					*12 Older adult COPD patients
<24 HOUR DIURNAL What are the energy measurement differences between measurements performed on the same individual over various time periods assuming resting conditions and control for diet-induced thermogenesis, physical activity and body composition are followed?	In healthy adults, repeated measures of RMR during 24 hours under fasting conditions or patients with continuous enteral or parenteral feedings vary on average around 5%.	II	II
> 24 HOUR DIURNAL	Measures of RMR in weight-stable, nonobese and obese individuals repeated after >24 hours will be within 10% of each other, with an individual variation of 0-310 kcal/day.	II

Table 4.3: Considerations After Measurement

Evidence Analysis Question	Conclusion Statement	Evidence Grade						Comments
Evidence Analysis Question	Conclusion Statement	Healthy Adults	Adult Patients	Institutionalized (transitional care, sub-acute)	Acute/ Trauma	Critically ill/Ventilated	Ethnic Populations	Comments
HORMONE VARIABILITY: Do circulatory hormones that target cellular metabolism have a significant effect on RMR during or after hormone level changes resulting from aging, birth control medications, or selected medical treatments [i.e., hormone replacement therapy (HRT)]?	Aging: In men after age 41 years, group mean rate of decline is -10.9+0.61 kcal/day per year, while women’s rate of decline is -5.48+2.1 kcal/day each year after age 51 years. These declines are not fully explained by losses of fat-free mass (FFM).	II
HORMONE VARIABILITY: Thyroid	Thyroid-stimulating hormone, thyroxine, and triiodothyronine: Thyroid hormones are correlated with RMR in non-obese and obese men and women but only explain 1-9% of RMR variation; the correlations disappear after controlling for FFM.	II
HORMONE VARIABILITY: Thyroid	In individuals who have lost weight (i.e., post-obese) or are known to have subclinical levels of thyroid hormones, there were no statically significant correlations when RMR is adjusted for lean body mass.	III
HORMONE VARIABILITY: Estrogen, Estradiol, and Progesterone	Group mean RMR is increased 48 kcal/day in the luteal (post-ovulation) vs. follicular phase of the menstrual cycle and individual variability over the entire cycle ranges 2-10%. Oral contraception may increase group mean RMR up to 72 kcals/day but hormone replacement therapy does not impact RMR.	III
	Treatment of PCOS with ethinyl estradiol-cyproterone acetate may increase RMR in obese subjects, but should not be employed for energy balance management due to the associated deterioration of glucose control.	V
PHYSICAL ACTIVITY FACTORS* What physical activity factors should be used with measured resting metabolic rates?	Non-obese: With a mean age of 62.3 ± 16.0 years (21-90 y age range), the physical activity levels ranged from 1.01 to 2.32 [mean 1.61±0.31] with a range of activity from sedentary to very active.	III
	*Special Populations (Obese):* In 44 obese adults (13 M; 31 F) with a mean age of 63.7 (6.2) years, the physical activity levels ranged from 1.07-2.39 [mean (SD) 1.55 ± 0.28] with a range of activity from sedentary to very active.		III
	*Special Populations (Old and Very Old):* In 21 older adults (12 M; 10 F), with a mean age of 79.2 ±4.2 years and 75-90 years age range, the physical activity levels ranged from 1.12-2.11 [mean 1.52 +/- 0.27] with only 2 individuals representing very active physical activity levels.	III

*Note. The physical activity factors were not part of the indirect calorimetry evidence analysis and therefore did not undergo the same rigorous review process; however, these could be considered after the IC is complete as part of a patient/client’s nutrition care.