#136 - AMA #17: Body composition methods tour de force, insulin resistance, and Topo Chico

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Welcome to another Ask Me Anything episode. This is AMA number 17. I'm once again joined by Bob Kaplan, and he goes by a little alias on this episode. In this episode, we dive pretty deep into body composition. The question actually stemmed from, hey, what's the best way to measure body composition? But it digressed into what I think is a very comprehensive discussion of all the different ways that you can measure body fat. And there are more than you probably realize along with what it means. What's the difference between subcutaneous fat, visceral fat, what's the optimal body fat? What are the strategies around improving your health? Is it better to do it through a gain in muscle mass versus a loss in body fat, et cetera? And that takes up a heck of a lot of time. And it really only leaves time for one other major topic, which is one around insulin resistance. The question basically being, being, hey, is insulin resistance reversible? Which of course becomes a very long discussion and an opportunity, frankly, to showcase a cool little case study, which I do. We close this one out with a little bit of a discussion on Topo Chico. So if my recent email on Topo Chico piqued your curiosity, including my decision making around it and what my potential call it substitute agent, is that I'm now mixing in with my Topo Chico and alternating with, we talk a little bit about that. So without further delay, I Hope you enjoy AMA number 17. This is going to be a pretty cool ama. But I actually thought I was doing it with Bob Kaplan. Didn't realize I was going to be doing it with Mike Liute. What's going on here?

I'm donning the whaler's cap, so I figured that would be my alias today. That's usually when I check into hotels because my popularity, my celebrity, I usually check in as Mike Liute.

There's bonus points to anybody listening to this. Who knows who Mike Gliut is, but the fact that you and I both immediately know. Well, you know, of course, because it's your alias, but I immediately recognize it. I don't know. Is that Sad or it's impressive.

I'm wondering how many people will know who the Hartford Whalers are. It's been a while.

Let alone who their goalie was. Circa 1984.

Yes. And who they are now. They still exist, but they moved and they changed their name.

Yes, indeed. So what do we have on the agenda, Mike, or should I say Bob?

For today we've got a bunch of questions and I batched them. I think that's as per usual, into a few. But we've got some stuff on body fat measurements. There's so many out there. What's the best type to use? And do you have to buy your own dexa or can you get away with some of the handheld or the stand up scales that do the. We'll get into that. Questions around insulin and glucose and insulin resistance and whether you can reverse it. And then we got a bunch of questions around Zone 2. And then maybe more of a. Well, not a rapid fire, but there are a lot of questions recently about Topo Chico. I think more people will know what Topo Chico is than the Hartford Whalers and Mike Liute and then a couple other questions. One of the recent weekly emails was about colorectal cancer screening. And there are a lot of questions that you could grill your GI doc or your personal care physician. A lot of people are wondering, how do I do that delicately without them getting upset? I think we should just dig in from the top, which is body fat measurements.

I mean, I think for context, it's worth explaining why one would even care about that. We have a very crude measurement by which we can assess a person's health and it's called weight. So you could stand on a scale, you can measure a person's weight, and if you juxtapose that with their height, you can calculate something called a body mass index. And certainly the body mass index is proportionate to health in some way, shape or form. So we generally know that people with a body mass index in the vicinity of 20 to 25 are healthier than people with a body mass index, say between 35 and 40. That would be a relatively easy statement to make, but it doesn't really tell us a whole heck of a lot between the difference body mass index of 22 versus 26, for example. Do you know your BMI, Bob?

I do. It's probably. I am.

You got to be 27, 28.

Yeah, that's right. Probably around 27, 28.

Yeah. So technically you're overweight, aren't you?

I am, technically, yes, I am.

You are technically overweight, but as I look at you here on this screen today, you're a staggering specimen of muscle mass.

It helps. My shirt's off, right?

Yeah, yeah, of course. We always do topless podcasting only. So how do we capture that? Right, so how is it that we've got Kaplan over here at a BMI of 27 to 28, who, if you just went off an actuarial table, you'd say, oh my God, we got to do something about this. And I've got patients who have a BMI of 22. And you'd say, well, fantastic, high five, keep it up. But the reality of it is I'd much rather be in your shoes than theirs. What's that difference? Well, obviously a big part of that difference is muscle mass. And your muscle mass is such that your fat free mass, I guess is a better way to describe it, is the dominant part of what you are. And so your fat mass is actually very low. So most people now, I think by having this discussion, have a sense of what we're talking about, which is what percentage body fat are you? That becomes a much more interesting measurement. So to have a BMI of 27 at, you're probably at about 8% body fat is a far healthier place to be than to be at a BMI of 22 with 24% body fat, the sort of skinny fat phenotype. So we'll refrain from digressing into all the nuances of what all that means from a metabolic perspective, because I think your question was just how do you do this? And the point here is you have to be able to measure body fat somewhat accurately if you want to get to this next level of thinking. So there are lots of ways to do this. Let's go through many of them, including ones that are really not necessarily things I'd recommend for people think about doing.

The best one that you probably wouldn't recommend, which I think cadaver analysis, that's the most precise.

The most precise would be burn calorimetry, where you would combust an individual after they were deceased. And by measuring the constitutive amounts of oxygen consumed and CO2 released, yes, you could get a pretty good guess of their body fat. So shy of that amongst the living, magnetic resonance imaging or MRI would probably produce the most accurate results. I have only had one body fat test in my life done via MRI or two, but it was part of an experiment I was participating in. So this is not something that is a typical indication for mri. It's usually done in the research setting. Did we ever do an AMA on how MRI works?

I think Raj was on the podcast, so.

That's right. That's right.

He dug into it. This is probably getting ahead of myself. But one of the things we're going to look at is dexa, which is an X ray. But people will often get that to look at their bone mineral density. And you can also get body fat. I think a lot of people will go in for their bone mineral density and the software package will spit out and they'll tell them what their body fat percentage is and all that other stuff. We can get into that. But I'm curious, with an mri, when you get into an mri, if you go in for an MRI for another reason, you're not also going to get as part of that package, oh, by the way, here's your body fat percentage.

Very rarely do people go in for a whole body mri, and even if they did, there would be a big software look that would have to look specifically at the protons within fat. It wouldn't be impossible. And who knows, as time goes on, maybe more and more whole body MRI centers will be spitting out that information for free, as the way you described it in other technologies. But again, when most people go to get an mri, it's hey, my knee, my back, my this, my that, where you wouldn't be able to capture all of those data. Because a whole body MRI is a stupidly time consuming process unless you're doing it via one of the very, very, very few technologies that can do it.

In under an hour.

Most typical commercial grade scanners would take four to six hours to scan the whole body. All that said, let's not get into how MRI works. It's the gold standard. And the reason it's the gold standard is not just how accurate it is, but frankly, that it gives a very, very clear picture of where said fat is. And this is a point worth mentioning, not all fat is created equal. I think for the purpose of this discussion, we can put fat into two buckets, though I really think there's a third. We can divide it into cutaneous or subcutaneous fat, fat that is beneath the fascia known as visceral fat. And I think most people have heard that term because most people probably appreciate that visceral fat is the one you don't want. So it's one thing if you can't see the six pack of abs, but to be clear, the inability to see the six pack of abs is really an issue of either too small A rectus abdominis muscle group and or too much subcutaneous fat surrounding the rectus abdominis muscles. No six pack equals one of those two things or a combination of them, but it doesn't tell you what's happening beneath the fascia. So you have this corset that is holding you together that is beneath your muscles and it's called fascia. And it's inside that fascia that all of your organs exist. And that's the place where you don't want to see any fat. Where this fat typically shows up is around the liver, around the kidneys, around the spleen, around the gut. That fat is incredibly associated with metabolic disease. If we were going to track people by some metric, it wouldn't be bmi, it wouldn't be weight, frankly, it wouldn't even be body fat percent. It would be total amount of visceral fat in some normalized way. If everybody walked around knowing, hey, I've got 6.3 pounds or whatever of visceral fat, or 4.2% of my body weight is visceral fat. And we tracked and managed that, holy cow, we'd be in a much better place. And MRI allows that, so it can very clearly distinguish between these compartments. Also, something about MRI that's fantastic. It's non invasive, produces zero radiation. So you could MRI yourself all day long and you're not gonna have that issue. Of course, on the flip side of that, again, I just think this is a new application for mri, not necessarily practical and obviously from a cost and availability perspective, sort of not the way to go.

Do you have like a ballpark of how much? If I wanted to get an like next to my barrel sauna, I want to get an MRI machine. How much it might cost?

Sure. For giggles. So if you wanted to buy. So it's about a million bucks a Tesla. So if you said you wanted to slum it and get a one Tesla mri, which would be a super low end MRI today, that would cost you about a million bucks. Plus hiring someone to run the thing. I don't know. I don't think of it as a great investment, Bob.

It would be good at dinner parties though, when somebody says, I have a Tesla. And then I'll say, well, I've got a version of that too as well. In the back you could say, I've.

Got a 3 Tesla, I've got 1.5 Tesla. Yes, there you go. Which I think is the sweet spot. Okay, so moving down from mri, another way to measure body fat is actually to Use CT scanning. So a CT scan is another type of scanner that you get into. Just like an mri, they tend to be a heck of a lot faster. So you can CT scan the whole body much quicker than you can do so with an mri. And like the mri, the CT scan does a very good job of showing fat, so you very clearly get to see where the fat lies because it's a really, really good anatomic study. And it basically can show you this is intra abdominal, this is subcutaneous. And so you again have that tool to kind of quantify not just how much fat the person has, but more importantly where that fat resides. Now here you have less of an issue on the cost side, but the far bigger problem is radiation. And in fact, I would never recommend a whole body CT scan. Honestly, I can't think of a single indication I would ever consider whole body CT appropriate. And it's amazing because years ago there were all these places popping up on street corners saying, hey, come on in for your whole body CT scan to check if you have cancer. Which is the greatest irony of all, because God knows how many cancers you are predisposing people to with those things. I suspect in a whole body CT scan would be 50 millisieverts of radiation, which is about the annual allotment that is recognized for a human being. And obviously you don't want to be near the annual allotment on one day. But conversely, just getting a CT scan of the chest, abdomen and pelvis, which lots of hospitalized patients need, could easily expose you to 10 to 20 millisieverts. I'd like to live my life in a sub 10 millisieverts per year environment, if possible.

You don't want to be an astronaut, Peter?

That's a good question. I mean, somebody knows this. And of course, even though they're wearing unbelievably protective equipment. Do we know how many millisieverts someone would get a year at the iss?

I think we do. I can look it up. We can include in the show notes we've got that chart with the different radiation millisieverts.

Yeah, Just standing at sea level for a year, you're probably getting 2 to 4 millisieverts. And if you live at elevation, you know, if you're living in someplace like Denver, you're probably almost doubling that, but you're still well below 10. You want to use CT scans judiciously and there's a time and a place for them, but measuring body fat ain't it. Okay, you then alluded to something called dexa, which sometimes goes by dxa. It's dual energy X ray absorptiometry thank.

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