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Energy Considerations

by Georgina Cornwall, PhD
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    00:01 In this lecture we will be reviewing some of the energy considerations relative to nutrition that you need to have right in your pocket for your medical licensing exams.

    00:12 These things include basal metabolic rate as well as body mass index, total energy expenditure, as well the fuel caloric values and so forth.

    00:23 So moving into - looking at basal metabolic rate, most often we'll consider resting metabolic rate.

    00:30 Because it's the much more simple measurement to make.

    00:33 Resting metabolic rate doesn't take into account having to have 12 hours of fasting and necessitate 8 hours of sleep.

    00:42 It's a simple measurement taken upon waking and getting up.

    00:47 So resting metabolic rate is generally, we use in an equation to calculate our basal metabolic rate.

    00:57 But if we are going to do it very clinically, we would measure the VO2 at various times, on various days.

    01:05 But again we will generally use an equation to calculate basal metabolic rate.

    01:11 And I'll introduce you to or help you review two of them that will be important for you to keep in mind.

    01:18 This first one, you probably just need to know the name of.

    01:23 But if you want to go beyond that, you could memorize the equation.

    01:27 We're not going to spend the time deriving it.

    01:30 But it takes into account the age of the individual as well as the gender weight and height.

    01:36 And you can see that there is an adjustment over there on the right hand side based on the gender.

    01:43 Whether it's a male or a female.

    01:45 And again you don't need to understand where the numbers come from.

    01:50 It's a plug and chug kind of thing, Measuring height in centimeters and weight in kilograms.

    01:55 More commonly, these days though the Katch-McArdle formula is utilized in which we consider pretty standard numbers.

    02:06 Basal metabolic rate equals 370 + 21.6 times the lean mass in kilograms.

    02:13 The catch here is that we have to know the body fat percentage.

    02:18 And that turns out to be not so difficult to ascertain these days.

    02:23 Of course you can do Caliper testing but there are bioelectrical impedance devices that patients can just hold on to and we get a fairly decent estimate or at least relative estimate of the body fat percentage.

    02:35 So we can calculate lean mass by subtracting the body fat percentage.

    02:42 So Katch-McArdle is the one I would certainly commit to memory and keep in your pocket for use on your exam.

    02:49 Now total energy expenditure is the energy we use beyond our basal metabolic requirements.

    02:58 Plus, all the other things that we do in a day.

    03:02 So all our caloric needs over a 24 hour period, first of all you probably realize but maybe haven't thought about it in the total energy expenditure realm.

    03:14 That when we consume food it actually costs as calories to consume and digest that food.

    03:23 So that is the thermic effect of feeding.

    03:26 And that's about a 10% of our total energy expenditure in a day.

    03:31 Now of course in addition to that we have some physical activity.

    03:35 Some of that physical activity is activity that we choose to do as we move around.

    03:40 But even when we are sitting still, we are still burning calories.

    03:46 And we need to add this physical activity, whether it's intended exercise or general mobility, we need to add this to our basal metabolic rate.

    03:59 So there's the component of physical activity that we call NEAT.

    04:05 Another term you should be familiar with.

    04:07 Which is our Non-Exercise Activity Thermogenesis.

    04:10 So this is when your sitting at your desk and you feel like you're doing nothing and not burning any calories.

    04:16 In fact, we are burning calories during that because we have to have muscles firing to keep us upright and not in a pile on the floor.

    04:24 So all of these pieces go into the calculation of total energy expenditure.

    04:30 And then how do we calculate the physical activity piece of this.

    04:37 This is can be pretty controversial calculation I suppose because as always when people give us numbers, they vary from source to source.

    04:47 But in general we will take our basal metabolic rate and multiply it by a certain factor dependent on the activity level.

    04:59 So someone who is sedentary will have a lower factor to multiply by than someone who is particularly active.

    05:05 Again you'll see a vast difference in the actual figures provided.

    05:11 What I recommend is that you get a perspective of what sort of factor it is.

    05:17 So somewhere between 1 and 2.

    05:20 However, we really know that there are extreme athletes.

    05:24 People that are riding century rides.

    05:26 Ultrmarathoners might run 50 miles in a day.

    05:30 They are certainly going to be above the extremely active level.

    05:35 So you might even see numbers towards 3.

    05:37 So don't go memorizing the numbers.

    05:39 Just sort of get a relative idea that physical activity is multiplying the basal metabolic rate by a particular factor.


    About the Lecture

    The lecture Energy Considerations by Georgina Cornwall, PhD is from the course Nutrition.


    Author of lecture Energy Considerations

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD


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