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Welcome to ask me anything episode number 40. And once again, joined by Nick Stenson, in today's episode, we talked about how to interpret dexa scans. We've had a lot of questions about this. I've talked about it on, and off in various podcast, both my own and being a guest on a few other podcasts. So we decided to kind of go through this, in the exact way that we go through.
Our patients. So what are the four things that a dexa scan tells us and how do we interpret each of these things? We then go through, I think about for patient case studies, Each of which is a luster t''v. Again, the likelihood that you will find something of yourself in at least one of these is very high and I think justifies going through all of them, we then kind of talked about protein because one of the things that comes out of interpreting the dexa scans is how do we assess a person's lean tissue and what we need to do about it. So then kind of answer a whole bunch of
Questions that came in about protein. How much do you need? When do you need it? How should it be divided throughout the day? We then close the discussion out with a revisit of time restricted feeding. I've made some comments in the past. I think most recently on the strong convictions, loosely held up a sewed where I talk about my changing views on trf and I wouldn't say it's that. I'm saying that one should never do trf, but I have a much more nuanced view of it today than I did five years ago. And I go through both the recent new.
Real medicine paper that came out earlier this year, that generated a lot of controversy and then add a lot more color to it, including a discussion about circadian rhythm and the relationship of food on the ability to sleep and even some brain health stuff. So if you're a subscriber and want to watch the full video this podcast, you can find it on the show notes page. And if you're not a subscriber, you can watch a sneak peek of the video on our YouTube page. So without further delay, I hope you enjoy. Am a number
for you.
Welcome to another am a how you
doing doing very well. Excited to talk about this stuff today.
Awesome, I don't know if you noticed, but I saw your Instagram post today on Maui newly venison. So I wore my access to your Institute shirt.
I wondered if that was a coincidence but
The Accidental experts love that story. So for today's am a it's not going to be on exercise, like the past who have been we're going to stick to that although I'm sure.
Are some of what we'll talk about will tie in a little bit to exercise. But what we're going to do is we just kind of gathered a ton of questions all around, basically body composition and one way or another. So we're going to start by looking at dexa scans. This is a topic that has come up a lot in amas recently especially the bone health AMA and we've gotten a lot of feedback from listeners who they're like hey I went and got my decks results, I'm trying to understand what they mean. How should I think about them? What matters, what doesn't
So we kind of compiled those and we're going to do a deeper dive into that including looking at some real-life patient case studies. So what we had is the team pulled specific patients that you have and we thought were kind of good overarching studies that kind of show people how they can think about this and then also what changes need to be made based on those results. So kind of not only how to understand the dexa but then how you apply that to your life and then from there we're going to do some follow-up questions.
That mainly came from the strong convictions, loosely held podcast and really around your comments on protein consumption and really how you get as much protein and throughout the day as you want to, and then also some follow-up questions on your comments, regarding your views on time, restricted feeding. So, it all goes to according to plan, we'll wrap all that, but I think it will all kind of fit together because I think a lot of what we'll talk about in the protein time. Restricted feeding will play off what we learn in the dexa.
So with that said anything you want to add before we kind of jump into the first question? Let's go for it, perfect. So the first one, keep it simple. Just how should people interpret their dexa scans? So when your patients do them and you do them and you look at the results, what do you care about? What are you looking at? And even what metrics are they providing that you don't care about
pray first. I should explain what a dexa scan is for folks with next your skin.
Is, it's an x-ray. Basically, it's sort of a moving x-ray, so you lay on a table and a really, really low powered x-ray. So, meaning very little ionizing. Radiation is sort of run across your body. And the way all x-rays work basically is, there's a plate behind the object, or the person being x-rayed, and it's effectively looking at what's hitting the plate, and the more dense something is in front of the plate. The
Less electrons that are going to hit the back of the plate. Now, there's a unit in radiation that we talked about and it's usually millisieverts, we talked about how many millisieverts of radiation. Something offers you and more radiation to some extent is harmful. And so, the NRC recommends that a person receive no, more of 50 millisieverts in a year and calendar year. So the question is, then how do you put that in context, right?
Oh, just living at sea level, is something to the tune of 122 millisieverts per year, so just being exposed to the Sun at sea level, not just the Sun, but of course, everything that's ionizing in space. Basically, it exposes you to three, maybe four percent of your annual allotment and that changes. So, if you lived in Colorado, you know, where you're basically a mile above sea level, it's about twice that amount that you're getting. But when you start to look at something like a,
Flight. Like what is an East Coast to West Coast Flight? Well, you know, it's a certain amount of radiation. It's not nearly as much as if you're going over the poles. But now you have to measure those things in microsieverts, that's how much lower it is. So a flight would be like 40 micro sieverts and again, a micro sievert is 1/1000 of a millisieverts. What about a mammogram? So mammogram would be about 400 micro sieverts or point for millisieverts, chest x-ray, depending on the size of the individual, maybe 25
50 micro sieverts conversely. A CT scan of the chest abdomen and pelvis could be up to 20 millisieverts which will be about 40 percent of your annual allotment. So, why am I saying all this? Well, I just want to put dexa in context because it is a virtually radiation-free technology. It is insanely low, I won't get into all the details of why, but it's typically less than 20 micro sieverts, that's sort of the punchline. So a dexa has no
more radiation than even the lowest end of a chest x-ray. And we're talking about gosh, like 1/20 of the radiation of a mammogram and about half the radiation of a cross-country flight. All that is to say, the dexa is a really safe, low risk. There's effectively zero risk to a dexa, scan and it's not something you need to do that often. We have some patients when they come to the practice, their ordering dexa, scans, or they've been doing dexa scans on themselves every six weeks, that's a total waste of time. This is a type of scan that
Would do once, maybe twice per year, it has the capacity to distinguish, effectively three things, bone, fat, and other. Those are basically the three buckets that dexa is distinguishing based on the density of what the electrons are going through. So when you do this, can you basically get four pieces of information if you're looking closely at it. Now again, when most people go and get a dexa, scan, their kind of looking at one thing, which is what's my body fat,
And again, body fat can be calculated in two ways but probably the best way to do it is to take the total amount of fat and divided by the total mass of the individual. And that gives you percent body fat, technically you can subtract out bone mass when you do that and get tissue fat percent but and by the way that doesn't differ very much because bones don't weigh that much just in case you're wondering where the discrepancy can be so certainly body fat is a relevant consideration will talk about it but I think there's three others that are more important and the first is actually
MD bone mineral density. That is both reported in an absolute amount in grams per centimeter squared, and it's also reported in a z-score. Now I think we'd probably covered a lot of this in the previous am a on bone health so I won't go into any more detail on that. The next thing that you get is an estimate of vat or visceral adipose tissue
again I won't
go into how this is done but it is clearly just an estimate and it's based on looking
At the amount of fat that is in the Torso above the anterior, superior iliac crest, and the ribs, and kind of, trying to subtract out what it believes is in the subcutaneous space. And therefore, looking at the difference and as you'll see, visceral fat is a relatively small fraction of total body fat. But it's important to get that right? Because it's so much more indicative of risk and the final thing
It gives you is, sometimes it does this directly, it just tells you the appendicular lean mass index and sometimes you just have to calculate it. And you can always calculate the fat free mass index with both of which we'll talk about. So, these are measures of how much lean mass. You have more muscle mass in the extremities. And the way this is always reported is total amount of lean tissue divided by height in meters squared. So, both appendicular lean mass index and fat free mass index which is just total
Mass that is not fat divided by height in meters squared. They're both reported therefore in kilograms per meter squared. So those are the four things you get when you do a dexa. And of course, all of these things you want to see how you stack up against a population and that population is typically stratified by your sex and by your age. So therefore we have Noma grams for each of these things. And that's how we present the data to a patient and that's how we therefore make decisions about where
You rank and what you need to do,
so to clarify on that. So the bone mineral density to that am a l.a. my and FFM. I those are the four major things and now I think I've heard you say before, is not every place you get a dexa, scan will give you those metrics, but every place will provide the metrics. You need to come to the conclusion of that for
yourself with one exception. So, there are some decks of places that only
Give total body z-score for bone and they don't break it out, individually by hip and lumbar spine. This is important because again, I believe I spoke about this on the previous. Am a. You can't make a diagnosis of osteopenia or osteoporosis, or frankly, assess, bmd clinically without that feature. In other words, if you just look at total body, bmd the Z score, for the total body is too easy to
Ask what's going on in those areas. So it doesn't mean you can't get a deck set one of those places you can, but you just have to understand there's a blind spot which is you're not getting adequate information about bmd. So, if there's any concern about bmd, you're going to have to go to a place that is able to give the segmented information, which is good for people to know just because
as they're Googling different places and calling around, it gives them some specific to ask for it to get a good understanding. Yep. So on that I think what makes sense do next
It is dive into each of those four metrics a little more, and kind of what they mean and why they're important with bmd is you mentioned we covered that in a bmd AMA, which was am a 37 for anyone who hasn't listened to it and wants to go back and listen. I don't think we really need to dive into that in as much detail. Just based on that am a, but the vat, a l.a. my, and FMI, I think might be worth getting into because I think those are metrics that. Most people aren't hearing about where body fat.
Energy. I think everyone is where that they conceptually know what that is. But the other three I think for people not in the space, it's a little outside of their understanding.
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