TDEE Across Lifespan
In the first episode of our new short Bonus Episodes, Coach Chris dives into the groundbreaking study by Pontzer et al that looked at Daily Energy Expenditure Through the Human Life Course. We talk about the design of the study, the findings, and what the practical applications for people is. The study can be found at: https://pubmed.ncbi.nlm.nih.gov/34385400/
TRANSCRIPT
CHRIS:
We need like a new... you know how there's that sound of Krissy introducing BIN Radio? We need one for this one.
ACACIA:
Oh, yeah.
Welcome To BIN Radio: The Weekly Study with-
CHRIS:
[doing a loud radio announcer impression] I'm your host, Chris Bonilla. But then my voice in the podcast is totally different.
[INTRO MUSIC]
ACACIA:
Welcome to BIN Radio. I am one of your hosts today, Acacia. I'm here always. Unfortunately, Ryface is not here with us
today. And our guests today, as we are launching a new series for our podcast, is Coach Chris. Chris, how are you?
CHRIS:
I'm really good, thank you. How are things with yourself?
ACACIA:
You know, I'm fine. I'm here in lovely Chico, California, which is my place of birth. And I'm here because my dad's celebration
of life is on Saturday. And I'm at this lovely coffee shop with this nice view of downtown. And we're just trying to do life.
CHRIS:
Oh, cool. Yeah, I'm here in a not-so-sunny Frederick, Maryland, trying to stay dry and get through the workday. So that is
exciting. But, you know, same same.
ACACIA:
Sounds great. We are doing a new series for BIN Radio, and it is going to be called "The Study of the Week." And Chris is go-
ing we are going to be doing these short episodes once a week talking about different studies and bringing some (hopefully!)
knowledge bombs to our wonderful audience that supports us.
And, you know, if you don't like our podcast please don't give us a review. If you do like our podcast, definitely give us a
review! And this week study is all about total daily energy expenditure a.k.a TDEE across the lifespan. And this is a study
that was done by Pontzer et al. And Chris is going to go over this study and we're going to talk about this over the next 20
minutes or so.
CHRIS:
Perfect. Yeah. Thanks for the intro. So, yeah, just piggybacking on what you already said. So the goal with this segment is to
take an interesting study, critically evaluate it, place it in the context with the other research in the field, and then hopeful-
ly provide some actionable takeaways for the everyday person, if there are any.
You know, sometimes we might just have to say, "this is interesting, but we can't really conclude anything major from
this," which in my opinion it's just as important of a conclusion. So yeah, my desire is to make some of the most important
research a little more accessible to the average person by simplifying concept as much as possible while still maintaining
the integrity of the information.
ACACIA:
Beautiful!
CHRIS:
So without further ado, today's study is titled "Daily Energy Expenditure Through the Human Life Course," by Herman
Pontzer and colleagues. And like the title suggests, this study sought to quantify the differences in energy expenditure as
we age and attempt to identify what factors determine somebody's energy expenditure at any given time. Whether it be
age, physical activity, sex, lean body mass, et cetera.
Now, whenever you see a study with a really ambitious title or people citing a study with very ambitious claims, you always
want to think to yourself what kind of study design, what kind of sample size or similar variety would you need to really
answer a question like the title poses? Are they going to do some kind of meta analysis of energy expenditure studies in the
literature, some of which use less reliable and less applicable methods of energy expenditure measurement? Are they going
to gather a few people from each age group in the lab for a few days and then measure their energy expenditure and then
just make extrapolations from that?
For something like this to truly make a meaningful splash and have applications to the everyday person (which, if you'll
remember, is the stated purpose of the segment), you would have to collect data from thousands of participants from all
around the world with an extremely accurate method of energy expenditure measurement.
You'd have to have valid data for fat-free mass, fat mass, sex, age, for all these thousands of participants. You would need
participants from newborns all the way to centenarians. I mean, it would be a truly huge undertaking to tackle the sort of
question that the title of this paper poses. And brother, let me tell you, that's exactly what happened here.
So let's let's get into the methods and I'll tell you exactly what they did here. The data for this study was taken from the
IAEA, doubly labeled water database, which is composed of 6743 measurements of energy expenditure using doubly labeled
water-and that was the number at the time of the study I just look this morning at the database and it's like over 7000.
So it's something that continues to grow, something that researchers can use as a resource to continue to do this type of
analysis. Just a really cool resource. Anyways.
So. Doubly labeled water. Let me tell you why this is significant. This method is really the gold standard in the field for ener-
gy expenditure, for measuring energy expenditure for a few reasons.
The way it works: Participants come to the lab and they drink a very precisely measured dose of water that is enriched with
certain hydrogen and oxygen isotopes. And then once they drink this water, they're then sent off to go to live their normal
lives for a few days, and when they come back, they pee in a cup and we can measure their rate of CO2 production by
observing the rate of depletion of those isotopes.
And then from that CO2 production, we can determine energy expenditure. So this method is extremely accurate and has
the advantage of allowing participants to be free living during measurement, which gives us some more generally applicable
data points than if we just lock them up in a metabolic ward and used something like indirect calorimetry because people
don't do their normal everyday activity exercise wise if they're locked in there like that. The downside of the method is it's
extremely expensive. So being able to analyze thousands of samples like this, it's a pretty huge deal.
So a quick summary of the findings: Fat Free Mass was really the only reliable predictor of energy expenditure during each
stage of life. However, there were four distinct phases of life identified where fat free mass adjusted energy expenditure. So
think "calories-burned-per-pound of fat-free mass" is markedly different.
Those four phases:
The First Phase is going to be the first year of life- from newly born to one year old energy expenditure accelerates pretty
rapidly and peaks at about 46% above adult values. And then energy expenditure declines slowly throughout adulthood and
adolescence.
The Second Phase: From about one year old to 20 years old.
The Third Phase: Your energy expenditure then remains very stable from about 20 year old all the way to 60 years old, and
that's including during pregnancy, which blew my mind.
The Fourth and Last Phase: was 60 years plus, in which you do see a slow decline.
The biggest surprise here is the age within those four stages did not seem to affect energy expenditure and neither did sex
when controlled for fat-free mass. And even pregnancy status- when you account for the fat free mass of the fetus inside,
didn't affect energy expenditure- which was just absolutely wild to me. Although I remember when my wife was pregnant,
her doctor told her the whole eating for two thing she really liked it should really be more like eating for 1.1 which actually
quick which kind of jives pretty well with the findings of the study.
ACACIA:
Right.
CHRIS:
But important caveat here. If your doctor tells you to eat more or less than this while pregnant listen to your doctor and
not some guy a podcast discussing a single study. Yeah. So before I get into any practical takeaways, I want to give you the
opportunity to ask any questions if you have any.
ACACIA:
What was it that drew you to this particular study?
CHRIS:
Yeah. So when it came out last year, it made a pretty big splash in the nerd field of fitness and nutrition, but it really made
an impact on me because it challenged a lot of the notions that I held previously with sex, age, and all these things I would
think just intuitively had a big impact on energy expenditure.
So whenever I see something that challenges my preconceived notions that upon further evaluations were only based on
anecdotal evidence, then that's always kind of a wake up call like, "Huh, this is worth looking into."
ACACIA:
Science is ever developing and as coaches, it's important for us to develop as it develops and be challenged, I think. The
field that we are in, if we look at 30 years ago, nutrition has changed in some really, really big ways. And we look at energy
expenditure completely different, or not completely, completely different, but pretty different than we did 30 years ago.
CHRIS:
Yeah, definitely. I think that brings up a good point where something I've tried to do a lot with myself is every now and then
do like a Belief Audit. You know, think about like some of my most strongly held beliefs and just think about, "OK, why do I
think this? Is it just because of some kind of bias I have or some kind of experience like that?" Or is it based on, you know,
empirical, objective evidence? And then just kind of always evaluating those things in my coaching practice, and just life in
general, really. I think that's important.
So anyways, yeah, let's get into some of the practical takeaways first. I think that whole the old adage of your metabolism
slowing down as you age, you know, it seems to be true, although it seems to happen much later than most people think.
I've talked to people who are like 35 and they're like, "Yeah man, when you hit 30, you can get fat just from looking at a
milkshake." But in reality what people are probably experiencing is, if they are actually experiencing decrease in energy
expenditure, it's probably as a result of a decreasing fat-free mass.
And it kind of makes sense because, you know, once people start their careers, start families, it's common for exercise and
lifting to become less of a priority and decreases, and then therefore fat-free mass will decrease very slowly over time to
where it's hardly a noticeable from day-to-day or month-to-month. And that's probably what's going on as far as energy
expenditure goes for most people.
The next takeaway- when I say every mass is the most reliable predictor of energy expenditure, what that doesn't mean is
that two people with the same amount of fat-free mass are going to have the exact same energy expenditure. If you look at
some of the charts in the study, one in particular, it's got fat-free mass on the X-axis and then energy expenditure on the Y,
you can see there's still a good amount of variability at any given every mass level.
But the overall trend is that in general, the more fat-free mass you have, the more energy expenditure there's going to be. I
don't want you to think you, the listener -I'm speaking to you individually- I don't want you to think that something is wrong
with you if like you're training partner is literally the same size and same muscularity as you but your maintenance calories
are like 500 calories less or something like that.
In fact, the authors of the study pointed out that on average you can expect about a ± 20% variance in energy expenditure
when fat-free mass, fat-mass, sex, age are all equated. For example, somebody with 50 kilos of fat free mass would on av-
erage, according to this data, have an energy expenditure of around 2800 calories. So a 20% variance means that someone
with that level of fat-free mass would use anywhere between 2400 and 3400 calories, which is a huge range, and that's
only within the normal variance that we see here with that 10%. If you look at the that same chart and kind of try to pick
out some of the individual data points, you can identify some really interesting outliers.
For example, that same marker of fat-free mass,-50 kilos- we establish the "normal" range was between 2300 and 3400.
But if we look at some of those outliers there are some folks at that same fat free mass who measured energy expenditure
as low as 1700 calories and as high as 4700 calories. Now this is probably the difference between someone who is com-
pletely sedentary versus like an endurance athlete or something.
And even then, activity level alone isn't enough to create such a large difference within the same fat free mass level. It's
probably more, it's more due to things like dieting status. You know, if you just made a huge cut from 70 kilos of mass to
50, you might be on the lower end of that spectrum. And then of course certain things like genetic factors, which I'm wholly
unqualified to speak on. So as a coach, it is important to keep in mind because, you know, whatever model or equation you
use to estimate energy expenditure, you're going to have clients who might be more like these outliers.
So while there could always be issues with tracking accuracy, and all these things which you can address, of course, even
then you might see some calorie intakes that don't quite "look right". But they could very well be accurate. So you just want
to keep in mind, I think, and that I always try to keep in mind.
Last thing. They also talk a good amount about the role of physical activity on energy expenditure, which I don't think should
be overlooked, but I think it'd be worth dedicating a whole podcast on that bit, especially since the main author, Dr. Pontzer,
is the guy who popularized the whole constrained energy model, which we can do a whole podcast on. He's also the guy who
wrote the book BURN, in which he talks a lot about this study and about the constrained energy model. So big recommenda-
tion for further reading on that. But yeah, that's, that's it for this study. Unless you've got anything else.
ACACIA:
You don't think so? I mean, I think that one of the biggest points is where we kind of get stuck at, you know, that saying
that's like, 30, 35 is when our metabolism stops and like everything goes downhill. And that's something that I've heard
forever, but it's not true.
I think it's important to look at that and realize that there are things that we can do to help ourselves. I think that's great.
And if you have any studies that you'd like Chris and I to go over, send them our way, you can always email us at admin@
blackironnutrition.com or send us a DM on social media. So yeah, we're here!
Yeah, it's like my DMs my, my Instagram is Chris.PaulBonilla and I'm always open for discussion. I love this stuff and thanks
for having me on!
ACACIA:
Perfect. Thank you, Chris. Have a wonderful rest of your Tuesday. Bye.
CHRIS:
Bye.