Chapter 24- Estimating Energy Requirements

1. Chapter 24- Estimating Energy Requirements Jacalyn J. Robert-McComb, PhD, FACSM

2. Learning Objectives Following this presentation, you should have an understanding of: • the components of energy expenditure; • methods of measuring energy expenditure; • average dietary reference intake values of energy for active individuals; and • estimated energy expenditure prediction equations.

3. Introduction to the Concept of Energy • Energy is defined as “the capacity to do work”. Energy is expended by the human body in the form of resting energy expenditure (REE), the thermic effect of food (TEF), and energy expended in physical activity also referred to as EEPA (Fray & Johnson, 2004; Institute of Medicine (U.S.), Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, 2002).

4. Components of Energy

5. Resting Energy Expenditure Resting energy expenditure (REE) is the energy expended in the activities necessary to sustain normal body functions and homeostasis. This energy encompasses respiration, circulation, the synthesis of organic compounds, the pumping of ions across membranes, the energy required by the central nervous system, and the maintenance of body temperature.

6. Factors that cause the REE to vary among individuals • Body Size and Weight (Body Surface Area), • Body Composition, • Age, • Sex, and • Hormonal status

7. REE • The main determinant of REE is fat-free mass (FFM) or lean body mass (LBM). • Because of their greater FFM, athletes or individuals who are extremely fit have approximately a 5% higher basal metabolic rate (BMR) than nonathletic individuals.

8. Methods of Measuring Energy Expenditure • The Doubly Labeled Water Technique (DLW) • Direct Calorimetry • Indirect Calorimetry • Surveys/ Questionnaires • The Seven Day Recall Physical Activity • Yale Activity Survey • Estimated Energy Expenditure Prediction Equations

9. The Doubly Labeled Water Technique (DLW) • This method uses two stable isotopes of water (deuterium [2H2O] and oxygen -18 [H218O]); the difference in the turnover rates of the two isotopes measures the carbon dioxide production rate, from which total energy expenditure can be calculated. • The DLW technique has many advantages; however, the expense of the technique makes this technique impractical for daily use by clinicians. • The primary advantage of this technique is its accuracy (2-8% precision) and that it provides a measure of energy expenditure that incorporates all the components of TEE, REE, TEF, and EEPA (1,9).

10. Direct Calorimetry • This is a method for measuring the amount of energy expended by monitoring the rate at which a person loses heat from the body using a structure called a whole-room calorimeter. • Direct calorimetry provides a measure of energy expended in the form of heat but does not provide information on the type of fuel being oxidized.

11. Indirect Calorimetry • This is a method of estimating energy production by measuring oxygen consumption and carbon dioxide utilizing a respirator gas-exchange canopy or ventilation hood. • Data are obtained from indirect calorimetry that permits calculation of the respiratory quotient (RQ= moles CO2 expired/moles O2 consumed). • Depending on the RQ value, energy per liter of oxygen will be converted

12. Estimated Energy Expenditure Prediction Equations • The National Academy of Sciences, Institute of Medicine (IOM), and Food and Nutrition Board in partnership with Health Canada, developed new prediction equations to estimate energy requirements (EER) for people according to their life-stage group • The EER incorporates age, weight, height, gender, and level of physical activity for individuals in various life-stages. • These equations should only be used as a guide to promote optimal nutritional status; the individual should be monitored closely to adjust caloric intake based on target goals and changes in body mass. • As in all prediction equation, standard errors are inherent .

13. Sample Equation • EER for Women 19 Years and Older (BMI 18.5-25 kg/m2) • EER = TEE • EER = 354 – (6.91 X Age [yr]) + PA X (9.36 X Weight [kg] + 726 X Height [m]) • Where • PA = Physical activity coefficient: • PA = 1.0 if PAL is estimated to be > 1.0 < 1.4 (Sedentary) • PA = 1.12 if PAL is estimated to be > 1.4 < 1.6 (Low Active) • PA = 1.27 if PAL is estimated to be > 1.6 < 1.9 (Active) • PA = 1.45 if PAL is estimated to be > 1.9 < 2.5 (Very Active)

14. Average dietary reference intake values of energy for active females individuals (non-pregnant) • 0-6 mo 520(3mo) • 7-12 mo 676(9mo) • 1-2 yr 992(24mo) • 3-5 yr 1642(6yr) • 9-13 yr 2071(11yr) • 14-18yr 2368(16yr) • >18 yr 2403‡(19yr) • ‡Subtract 10kcal/day for men and 7 kcal/day for women for each year of age above 19 year.

15. Summary A clinical decision of whether an accurate metabolic rate by measurement is required to provide nutritional care and counseling should be made on a case by case basis. If the target goals are not being met, the client should be monitored closely utilizing any dietary intake records, energy expenditure logs, and physiological measurements of body mass and or weight change. Indirect calorimetry may be an important tool when, in the judgment of the clinician, the predictive methods fail an individual in a clinically relevant way (Frankenfield, Roth-Yousey, Compher, et al., 2005 ).