Lab Exercise 8. Energy Expenditure (98 points)

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1 Lab Exercise 8 Energy Expenditure (98 points) Introduction To understand an individual s energy requirements, we must be able to estimate their usual energy expenditure. This is difficult to do in free living subjects without the use of expensive equipment and specialized facilities. However, we can make reasonable estimates of the components of energy expenditure to calculate an individual s total energy expenditure. We can consider total energy expenditure (TEE) to be comprised of the following components: the basal metabolic rate (BMR), energy expended due to physical activity (PA), the heat produced through the oxidation of food (TEF), and energy required for special metabolic circumstances (child growth, recovery from illness, pregnancy or lactation). In normal, healthy adults, we can describe total energy expenditure more simply using the following equation: TEE = BMR + TEF + PA where BMR refers to the basal metabolic rate; TEF refers to the thermic effect of food; and PA refers to the energy expended in physical activity. On average, BMR comprises approximately 65-75% of our total energy expenditure while the thermic effect of food comprises roughly 7-10% of energy. The energy expended due to physical activity and exercise varies widely between individuals, but on average comprises roughly 15-20% of energy. We can estimate BMR using predictive equations based on subjects height, weight, and age or based on an indirect calorimetry method in which oxygen consumption and carbon dioxide production are measured. We can also estimate energy expended due to physical activity through self report or via other methods that measure movement objectively, such as accelerometers, pedometers, or heart rate monitors. During this lab, you will: 1. Estimate basal metabolic rate from the Harris-Benedict equation. 2. Utilize your activity diary to estimate daily TEE, RMR, PA, and TEF. 3. Observe the application of a hand-held indirect calorimeter ( Body-Gem ) to measure resting energy expenditure Prior to lab, you must keep a log of your activities for 2 days (1 weekday and 1 weekend) using the Activity Diary posted on SmartSite. You must bring your completed log with you to lab in order to complete the remaining activities. 1

2 Part 1: Calculation of BMR and RMR 1. Basal Metabolic Rate (BMR) is the lowest rate of energy expenditure necessary to meet basic metabolic functions necessary for survival. Estimate your basal metabolic rate (BMR, in kcal/d) from your weight, height and age, using the Harris-Benedict equation. Record this information in the table below and show your calculations. Show calculations for full credit. (8 points) Harris-Benedict equations for predicting BMR in kcal: Men: BMR = (weight in kg) (height in cm) 6.8 (age in yrs) Women: BMR = (weight in kg) (height in cm) 4.7 (age in yrs) Sex: M / F Weight (kg) Height (cm) Age (yrs) Basal Metabolic Rate (kcal/day) Calculations: 2. Resting metabolic rate represents the energy expended when the individual is awake, often seated quietly after a 30 minute rest period. RMR is about 3% higher than the BMR. Using that assumption, calculate your RMR value. Show your work for full credit. (2 points) Part 2: Calculation of TEE 1. Prior to lab, record your own activities for two days (one weekday + one weekend) in an Activity Diary. Instructions and tables are posted on SmartSite. (20 points) 2. Calculate your total energy expenditure over two days using your completed Activity Diaries. To do this, you will need to refer to published activity factors, known as Metabolic Equivalent (MET) values to estimate the added energy expended during each activity. MET is defined as the ratio of work metabolic rate to a standard resting metabolic rate. In other words, 1 MET is the metabolic rate obtained during quiet sitting. MET values range from 0.9 (sleeping) to 18 METs (running at 10.9 mph). Reference tables have been published through the Compendium of Physical Activities website linked here: ( few examples are shown on the following page. The complete, searchable database is available on the website. Use that information to complete your assignment. 2

3 Activity MET value Lying quietly, watching television 1.0 Eating, sitting 1.5 Showering 2.0 Bicycling, leisure, 5.5 mph 3.5 Jogging (15 min/mile) 6.0 Using your Activity Diary, complete the sections under the blue headings. First calculate average resting energy expenditure per minute, by dividing your calculated RMR (under Part 1, question 2) by 1440 minutes. To determine the energy expended during each activity, you will need to multiply your RMR/min by the number of minutes spent in that activity, and the corresponding MET value for that activity. An example is below for a subject with an RMR=1400 kcal/d (0.97 kcal/min). It is not required that you show your work, but the example has it shown for you. Note that you should have 24 hours (1440 minutes) worth of data for each daily record. At the bottom of the table, sum the kcals per activity to obtain your energy expenditure for that day. (20 points) Time of day Activity No. of minutes 5:00 pm Bike home 20 5:20 pm Cook dinner 40 Selected Metabolic Energy Cost (MET) Selected Activity Bicycling, to/from work, self-selected pace Cooking or food preparation MET (multiple of RMR) Kcal/activity (MET x RMR/min x minutes) 6.8 x 0.97 kcal/min x 20 min = 132 kcal 2.5 x 0.97 kcal/min x 40 min = 97 kcal 3. Write the value for your estimated energy expenditure from your two days of records below. Then calculate value representing just your Physical Activity (PA) energy expenditure on those two days. Show your work for full credit. (8 points) Energy expenditure (RMR + Physical activity) from your activity diaries: Physical Activity energy expenditure (PA) Day 1 Day 2 3

4 4. What is your average daily MET? Calculate this number by averaging your energy expenditure of the two days and dividing by your RMR. For example, if your average energy expenditure is 2300 kcal and your RMR is 1400 kcal, your average MET is 2300/1400 = 1.6. Show your work for full credit. (2 points) Average MET: 5. The value you estimated for energy expenditure in your log needs to be inflated by a small amount to account for the Thermic Effect of Food (TEF). The TEF value is assumed to represent about 10% of an individual s Total Energy Expenditure (TEE) and represents the energy required to metabolize our meals. If we assume that TEE x 10% = TEF and TEE = RMR+PA+TEF, solve for TEF and TEE. Show your work for full credit. (8 points) Day 1 Day 2 Total Energy Expenditure (TEE): Thermic Effect of Food (TEF): 4

5 6. Compare the total energy expenditure with the energy intake that you obtained previously during the Diet Assessment Lab. (6 points) Day 1 Day 2 Mean of two days TEE (kcal/d) Energy intake from food records (Diet lab) (kcal/d) 7. How do the mean values for energy expenditure and energy intake compare? Are they similar or different? Using information presented in lectures or lab sessions, provide at least two reasons why you think the results are similar or different. (2 points) 8. Discuss at least two advantages and two disadvantages of the activity record as a method to measure energy expenditure. (4 points) 9. How might you use the type of information obtained in this lab and in the dietary assessment lab to counsel the following individuals on how to gain, lose, or maintain weight? List two different healthy approaches the individuals could take for each. (6 points) A female track athlete who has been told she cannot compete until she gains weight. A woman (BMI=33) who was recently diagnosed as pre-diabetic and needs to lose weight. A healthy 22-year old college student who wants to maintain his weight. 5

6 Part 3: Indirect Calorimetry Demonstration Indirect calorimetry is based on the principle that as fuel substrates (carbohydrate, fat, and protein) are oxidized, oxygen is consumed and carbon dioxide is produced. Thus, by measuring oxygen consumption (VO 2 ) and/or CO 2 production, it is possible to calculate heat production, or energy expenditure. Indirect calorimeters measure the gas ratios in the air inhaled and exhaled by the subject. Ideally, the measurement would be performed in the morning just after awakening to measure the basal metabolic rate. In practice, this is not feasible in free living individuals. In order to best approximate the measurement of BMR, the subject is asked to rest quietly for a standard period of time and then their resting energy expenditure is measured. During this activity, the TA will demonstrate the use of a portable hand-held device (BodyGem) that measures oxygen consumption, temperature, barometric pressure, and humidity to estimate resting energy expenditure. 1. Record the Resting Energy Expenditure (REE) data from one student volunteer in the space below. (2 point) Measurement Kcal/day REE from BodyGem 2. Calculate the subject s BMR using the Harris-Benedict equation. Show your work for full credit. (8 points) Sex: M / F Weight (kg) Height (cm) Age (yrs) Basal Metabolic Rate (kcal/day) Calculations: 3. List at least two reasons why these two numbers might be different? (2 points) 6

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