Nutrition Assessment
EE: Rest Periods in Healthy and Non-Critically Ill Adults
The registered dietitian nutritionist (RDN) should aim for a 30-minute rest period before starting a measurement of resting metabolic rate (RMR) in a healthy adult or those with stable COPD. If this is not possible, a 20-minute rest period may be sufficient. Research primarily in healthy adults showed that resting condition is achieved by the 30th minute of reclined rest, but studies that measured shorter rest times indicate that resting condition can occur in as little as 20 minutes in many adults. Individuals who move during the rest recovery time do not achieve a resting state by 20 minutes and may not be at complete rest at 30 minutes.
EE: Rest Periods in Healthy Children
The registered dietitian nutritionist (RDN) should aim for a 30-minute rest period before starting a measurement of resting metabolic rate (RMR) in a healthy child. However, if the child cannot cooperate with both a pre-measurement rest and rest during measurement, the RDN may choose to forego the pre-measurement rest period, initiate the RMR measurement immediately and then discard the first 10 minutes of data. Research in healthy children indicates that when doing so, RMR values recorded at the 20th minute of the measurement may be most indicative of rest in children. With this approach, limited evidence suggests that data recorded after the 10th minute are not significantly different from data at 30 minutes.
EE: Resting Activities in Healthy Adults
The registered dietitian nutritionist (RDN) should ensure healthy adults rest quietly and not engage in any activity during the 30-minute rest period. Some data suggest activities such as laughing, reading, or listening to music may increase resting metabolic rate (RMR).
EE: Duration of Measurement (Steady State) in Healthy and Non-Critically Ill Adults
When measuring resting metabolic rate (RMR) in a healthy or non-critically ill adult, the registered dietitian nutritionist (RDN) should discard the data for the first five minutes, and then use a validated steady state definition to determine the duration of the remainder of the measurement. The purpose of the discard period and steady state requirement is to minimize artifact in the measurement. Steady-state definitions vary by measurement length (four to 25 minutes), coefficient of variation (less than 5% to 10%) and combination of gas exchange variables (VO2, VCO2, RQ, minute ventilation).
EE: Duration of Measurement (Steady State) in Healthy Children
When measuring resting metabolic rate (RMR) in a healthy child who is unable to rest, the registered dietitian nutritionist (RDN) should include the rest period in the measurement, discard the first 10 minutes of data and then continue measurement until a steady state is achieved. With this approach, limited evidence in healthy children suggests that data recorded after the 10th minute are not significantly different from data at 30 minutes; data averaged around the 20th minute have the least variability.
EE: Body Positions in Healthy and Non-Critically Ill Adults
The registered dietitian nutritionist (RDN) should conduct resting metabolic rate (RMR) measurements in a healthy and non-critically ill adult in the supine position when possible. Research indicates that different postures affect RMR. One study of older patients measured prior to an elective thoracotomy reported that RMR was not significantly different in the 30-degree head-of-bed elevation compared to the supine position. In healthy individuals, three studies reported that sitting RMR was greater than supine RMR and standing RMR was greater than sitting RMR.
EE: Gas Collection Devices in Healthy Adults and Children
The registered dietitian nutritionist (RDN) may select any gas collection device (ventilated hood and canopy, mouthpiece and nose clip or face mask) for a resting metabolic rate (RMR) measurement in a healthy adult or child. Studies comparing the use of different devices are conflicting. The individual's comfort or preference should be considered when selecting a device, if possible.
EE: Diurnal Variation in Healthy Adults
The registered dietitian nutritionist (RDN) may conduct a measurement of resting metabolic rate (RMR) at any time of day in a healthy adult, as long as resting conditions can be achieved. Limited evidence indicates that diurnal variation has minimal effect on RMR in healthy adults.
EE: Room Temperature in Healthy Adults
The registered dietitian nutritionist (RDN) should minimize the effect of ambient temperature on resting metabolic rate (RMR) in a healthy adult, by keeping the room temperature between 22°C to 25°C (72°F to 77°F) or providing a blanket during the measurement. RMR measurements conducted at room temperatures 20°C or 68°F or less were higher than those conducted at 22°C to 25°C (72°F to 77°F). The use of a blanket minimized this increase. No studies were found that evaluated the effect of increased room temperature more than 25°C or 77°F on RMR.
EE: Noise Conditions in Healthy and Non-Critically Ill Adults and Children
The registered dietitian nutritionist (RDN) should measure resting metabolic rate (RMR) in a healthy or non-critically ill adult or child in a quiet room. Noise could adversely affect the measurement.
EE: Fasting Requirements in Healthy Adults
Prior to measurement of resting metabolic rate (RMR), the registered dietitian nutritionist (RDN) should ensure a healthy adult has fasted at least seven hours to minimize the thermic effect of feeding (TEF). Research in healthy adults indicates that the TEF dissipates depending on the amount of calories consumed. The TEF for meals containing approximately 450kcal to 1,500kcal is still present at three to five hours. One study reported that the thermic effect of consuming 1,300kcal was negligible after seven hours post-consumption.
EE: Exceptions to Fasting Requirements in Healthy Adults
If a seven-hour fast is not clinically feasible prior to measurement of RMR in a healthy adult, the RDN should instruct the individual that a small meal (300kcal or less) may be consumed four hours prior to the measurement. One study reported that the TEF, when consuming approximately 300kcal, was negligible after 3.5 hours post-consumption in healthy adults.
EE: Caffeine and Stimulants in Healthy Adults
The registered dietitian nutritionist (RDN) should ensure that a healthy adult refrains from ingesting caffeine or other stimulants for at least four hours prior to a resting metabolic rate (RMR) measurement. Ingestion of caffeine and other stimulants in healthy adults increases RMR for longer than four hours.
EE: Smoking and Nicotine in Healthy Adults
If a healthy adult uses nicotine products, the registered dietitian nutritionist (RDN) should ask the individual to abstain from such products for longer than 140 minutes prior to a resting metabolic rate (RMR) measurement. Limited research in healthy adult cigarette smokers indicates that there is a significant acute increase in RMR for at least 140 minutes after smoking. No studies evaluated the use of other nicotine-containing products.
EE: Very Light Intensity Physical Activity in Healthy Adults
If a healthy adult engages in very light intensity physical activity (e.g., getting dressed, driving, walking less than five minutes, etc.) prior to a resting metabolic rate (RMR) measurement, the registered dietitian nutritionist (RDN) should ensure a 30-minute rest period prior to the RMR measurement. Limited evidence in healthy adults reported that 30 minutes of rest is required for RMR to return to baseline after minimal activity.
EE: Light to Vigorous Intensity Physical Activity in Healthy Adults
If a healthy adult engages in light to vigorous intensity physical activity, the RDN should instruct the individual to refrain from physical activity prior to the RMR measurement for a period of time (e.g., 12 to 48 hours for moderate to vigorous physical activity). Physical activity raises the RMR for an unknown period of time in healthy adults after cessation of physical activity. The elevation of metabolic rate will vary based on intensity, type, duration, level of fitness and other factors. Therefore, the length of time that the individual must refrain from physical activity should be determined based on these factors.
EE: RQ Below 0.67 or Above 1.3 in Healthy Adults
If the respiratory quotient (RQ) falls outside the physiologic range (below 0.67 or above 1.3) in a healthy adult, the registered dietitian nutritionist (RDN) should suspect an error and repeat the resting metabolic rate (RMR) measurement. The physiologic range of RQ reflecting cellular metabolism across the fed and fasted state is 0.67 to 1.3.
EE: RQ Between 0.67 and 0.90 in Healthy Adults
If the RQ falls between 0.67 and 0.90 in a healthy adult, the RDN should accept the measurement because RQ values within this range cannot reliably be used to detect feeding protocol violations. RQ varies among healthy adults and the range of RQ between fed and fasted states overlaps. In individuals who fasted seven to 14 hours, research reports that RQ ranged from 0.68 to 0.90. Yet, in individuals who consumed a meal 2.5 hours prior to measurement, fasting RQ (0.79 to 0.81) increased by only 0.03 to 0.05. Research demonstrates that RQ has poor accuracy to evaluate feeding protocol violations.
EE: RQ Between 0.91 and 1.3 in Healthy Adults
If the RQ is between 0.91 and 1.3 in a healthy adult who has fasted, the RDN should suspect a problem and consider repeating the measurement. An RQ between 0.91 and 1.3 could be observed in an individual who has not fasted. However, it could also be due to an error in calibration, a leak in the calorimeter, a ventilation problem or some other artifact or protocol violation.
