# Energy Considerations in Nutrition: BMR, RMR & Physical Activity – Nutrition | Lecturio

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. These things include basal

metabolic rate as well as body mass index, total energy expenditure, as well the fuel caloric

values and so forth. So moving into – looking

at basal metabolic rate, most often we’ll consider

resting metabolic rate. Because it’s the much more

simple measurement to make. Resting metabolic rate doesn’t

take into account having to have 12 hours of fasting and necessitate 8 hours

of sleep. It’s a simple measurement taken

upon waking and getting up. So resting metabolic

rate is generally, we use in an equation

to calculate our basal metabolic rate. But if we are going to

do it very clinically, we would measure the VO2 at

various times, on various days. But again we will generally

use an equation to calculate basal metabolic rate. And I’ll introduce you to

or help you review two of them that will be important for you

to keep in mind. This first one, you probably

just need to know the name of. But if you want to go

beyond that, you could memorize the equation. We’re not going to spend

the time deriving it. But it takes into account

the age of the individual as well as the gender weight

and height. And you can see that there

is an adjustment over there on the right hand side

based on the gender. Whether it’s a male or a female. And again you don’t need to

understand where the numbers come from. It’s a plug and

chug kind of thing, Measuring height in centimeters

and weight in kilograms. More commonly, these days though

the Katch-McArdle formula is utilized in which we consider

pretty standard numbers. Basal metabolic rate equals 370 + 21.6 times

the lean mass in kilograms. The catch here is that we have

to know the body fat percentage. And that turns out to be

not so difficult to ascertain these days. 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. So we can calculate lean mass by subtracting the body fat percentage. So Katch-McArdle is the one

I would certainly commit to memory and keep in your pocket for use on your exam. Now total energy expenditure

is the energy we use beyond our basal metabolic requirements. Plus, all the other things

that we do in a day. 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. That when we consume food it

actually costs as calories to consume

and digest that food. So that is the thermic

effect of feeding. And that’s about a 10% of

our total energy expenditure in a day. Now of course in addition to that we have some physical activity. Some of that physical activity

is activity that we choose to do as we move around. But even when we are sitting still, we are still burning calories. 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. So there’s the component

of physical activity that we call NEAT. Another term you should

be familiar with. Which is our Non-Exercise

Activity Thermogenesis. So this is when your sitting

at your desk and you feel like you’re doing nothing

and not burning any calories. 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. So all of these pieces go

into the calculation of total energy expenditure. And then how do we

calculate the physical activity piece

of this. This is can be pretty

controversial calculation I suppose because as always

when people give us numbers, they vary from source to source. But in general we will take

our basal metabolic rate and multiply it

by a certain factor dependent on the activity level. So someone who is sedentary will

have a lower factor to multiply by than someone who is particularly active. Again you’ll see a vast

difference in the actual figures provided. What I recommend is that you get

a perspective of what sort of factor it is. So somewhere between 1 and 2. However, we really know that

there are extreme athletes. People that are riding

century rides. Ultrmarathoners might run

50 miles in a day. They are certainly going

to be above the extremely active

level. So you might even see numbers

towards 3. So don’t go memorizing

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

Interesting tutorial, nice and easy to listen to.

First place I've seen where it mentions using LEAN body mass instead of current mass in the BMR equation. Thank you for paying attention to that detail 🙂