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.