3 Reasons Every Cyclist Needs a DEXA Scan

If you’re like me, the number of hours of cardio on my Peloton and my mountain bike make me feel like I’m doing enough. How are we supposed to fit in gym time?

I do a lot of this: Zone Two for endurance, but also to burn fat. The question is, am I?

Because according to my Garmin scale, my percentage body fat is 33%. I call Bull. Here’s the thing: I didn’t know fat impacts VO2 Max. So, I decided to put my scale to the test with the gold standard: a DEXA scan. But, you know, the more I learn, the more I’m convinced that as cyclists, we all need a DEXA. We’re the kings and queens of cardio, but in other super important areas, we may not be. How do you know? Get a DEXA. And the good news is, it’s quick, relatively inexpensive, and you don’t need a doctor’s referral.

Recently, my 50-plus cycling group was surveyed, and you know what the number one struggle is? Excess weight. So, let me ask you, do I look fat in shorts? Wait, don’t answer that. You know you never answer that question. The truth is, we don’t know if I’m fat, well, not in the way that really, really matters. And that’s where the DEXA scan comes in. It’s an extremely low-dose moving X-ray, and what you get is a color-coded scan of your body and a detailed report that tells you your lean tissue, how much fat you have, and crucially, where it is, along with your bone density.

And because all our videos send me down a research Rabbit Hole, I’ve gone from “Well, this is going to be a fun test of our Garmin scale” to “Crap, am I fat? Like, in a way that’s linked to disease? I thought all this cardio was supposed to burn fat. Am I overnourished and under-muscled? I hope my bones are okay ’cause weak bones and mountain biking, not a good combo.” Nice.

Whoa, before I head out, I’m going to do one final weigh-in so we can compare.

Afterwards, I’m afraid that this is me, but I’m hoping this is me. Okay, I’m back, and I’ve got my report, and I’m feeling a lot better. But there is a bit of a plot twist. Not going to bury the lead here. I am not 33% fat. Garmin, like, it’s not even close. I’m actually 27% fat. And if 33% versus 27% doesn’t sound like a lot, that’s this 8 lbs of fat. But honestly, body fat is for newbs. What you really want to know, and what the scale can’t tell you, is how much of that is visceral fat—the bad fat.

Okay, so here’s the skinny on fat: the fat under our skin is called subcutaneous fat, you know, the “Can you pinch an inch or two” stuff. Well, really, that’s the least of your concerns. The other fat is visceral fat, located in your torso, and it’s the fat you don’t want. Here’s Dr. Peter Attia to explain why visceral fat is far more inflammatory:

“In fact, that’s part of the problem. You know, if we do a DEXA scan on a person, which is how you can measure some of this stuff, you do a DEXA scan on a person that weighs 200 lbs, that has 25% body fat, so by definition based on those numbers, they have 50 pounds of fat. But let’s assume that of that 50 pounds of fat, the visceral fat is 5 lbs, so 10% of their fat is visceral. That 5 lbs of visceral fat is wreaking all the damage in their body. The 45 pounds of fat that is not visceral, totally inert.”

His analogy nails it. The fat we carry under our skin is like a bathtub, just like filling up the tub with water, if you don’t shut the tap off at a certain point, it’s going to overflow, it’s going to wreak havoc in your home. Well, if you take in too many calories, at a certain point, your tub is going to overflow, and when it does, fat starts packing around your organs, here, in between the cells in your muscles, and even gets into your muscle cells. Dr. Gabrielle Lyon, who specializes in muscle and protein, puts it this way:

“For people to conceptualize this, it’s almost as if it’s a marbled steak. Yes, they’re just kind of gross to think about, but in fact, it does happen and is true. Not only does the muscle become ineffective in many domains of metabolism, it also becomes weaker. Contractile force is less, it is infiltrated with fat, and the quality of the muscle tissue diminishes. You put that in combination with an aging individual, you’re in trouble.”

The thing to understand is that my tub could be a dinky little clawfoot number from like 1900, and yours could be a freaking like four-person Jacuzzi. And that’s why some thin-looking people can be skinny-fat—metabolically unhealthy, tiny tub and too much visceral fat. And some people that look a little chunky can actually be metabolically healthier. Take me and Glenn—you’re objectively leaner looking than me, I carry some more fat over the hips and thighs, but I was sure that I was going to have a bit of visceral fat to deal with. That’s not the way it turned out—those little orange mattresses over my hips and thighs, that’s fat, and Glenn’s all muscle and bone. But if you look carefully, you’ll see that it’s Glenn that has more fat here in the Android or torso area than me. It’s more common with me. The important metric for this is the A/G ratio—Android, this is the Android region over gynoid, waist over hips. So, what does that mean? Well, for women, you want your A/G ratio to be under 0.8, and for men, you want it to be under 1.0. And so, that has put Glenn on the edge of concerning.

So, you’ve blown over—what do you do? Well, first, you see your doctor and make sure nothing serious is going on like inflammation or nonalcoholic fatty liver disease, or that your vitamin D levels—a hormone—aren’t low, because fat traps vitamin D so that it can’t be absorbed. Only a blood test and an ultrasound can tell you these things. Alright, so the next question is: how do you get rid of it? Well, here comes the good news.

The good news is that visceral fat shifts faster than the fat you can pinch—it builds up quickly, but it comes off quickly too. And good news, cycling is going to play a key role in this. But first, you want to check your DEXA report to see, am I under-muscled? I want to know how much muscle I actually have and how that compares to women my age. And as we discussed in this video, having enough muscle mass is the other side of the fitness coin, linked to living long and strong. And if you don’t hit the gym, you’re losing muscle mass every year starting as early as your 30s. Whereas the smart scale tries to estimate your overall muscle mass, A DEXA will provide you with your appendicular lean mass index or ALMI. All that means is that they add up the lean mass in your arms and your legs where there are no organs to mess up the data, to determine if you’re under-muscled or adequately muscled. My ALMI or RSMI, as it’s called in this report because they just can’t get it together and make it easy for us, is 7.5 kg over my height in meters squared. Women need to be over 5.45, and men need an ALMI of 7.26 or higher, otherwise, you are considered to have sarcopenia—degenerative loss of skeletal muscle. Your DEXA will also give you your muscle mass in each limb so that you can know if there are imbalances between right and left. But better yet, in a table I found online compared to women my age, it’s my upper body that needs work. Well, my leg muscles are over the 95th percentile, my arms are just a titch under the 50th percentile, which is pretty typical for cyclists. So now, I’ve got two goals: increase my upper body strength and lose a little bit of fat here in the Bonk region. And it may seem odd, but it’s here that I had a revelation about VO2 Max—you know, the cardiometric to rule the all, roll clip:

“How many people listening to us today do you think know their VO2 Max? Very few. There is no metric that I am aware of that is more highly correlated with the length of a person’s life than their VO2 Max. Why that particular metric? There’s probably two things going on, right? One, it actually does matter a lot. It’s an amazing proxy for health. Have you had a VO2 Max test done recently? Last one was probably four years ago. It is testing your maximal consumption of oxygen. Well, to get to that level, we are stressing you to the highest degree possible. The higher that number is, the more oxygen your muscles can utilize, the more fit you are, the more capacity you have to avoid illness. I think the other reason for it is that it’s a metric that is so ubiquitous, it’s very standardized. To have a high number, you must be exercising a lot, and we know the benefits of exercising a lot. The person who has a VO2 Max at the top 2% of their age, by definition, they’re doing a lot of exercise, and exercise has more benefit than probably any other single intervention we can do.”

As a reminder, Garmin says that VO2 Max is the maximum volume of oxygen you can consume in milliliters per minute per kilogram of body weight at maximum performance. Per kilogram of body weight, as in lose weight, increase VO2 Max. If you follow your VO2 Max and the related fitness A and you use the Gin Index scale Garmin uses, your weight and estimated percent body fat to make suggestions, like lowering your fat Mass could raise your VO2 Max. So, it’s not all about more HIIT workouts, more Norwegian 4x4s, more sprints—effort is literally one side of the equation. And then I read this on Runner’s World: the more fat you have, the lower your relative VO2 Max. In fact, fat mass is a better predictor of relative VO2 Max than exercise performance—how far and fast you go in the VO2 Max test. What this suggests is that the traditional relative VO2 Max is actually a combined measure of two different traits: how fit you are and how fat you are. Okay, so two things: remember, my scale overestimated my fat mass by 22%, and Garmin uses your estimated fat to calculate VO2 Max. So, I’m thinking my VO2 Max should be higher, and I’m even wondering, would it be higher if I didn’t use the smart scale? There’s only one way I’m going to know, and that’s a VO2 Max test in a lab.

But before we introduce even more data, the third big you want to zero in on on your DEXA is your bone strength or your bone mineral density. And here’s why: as cyclists, it’s super important for us to really know where we stand. Check out this study of male and female Elite cyclists from young to retired who were given DEXA scans: low BMD is highly prevalent in Elite cyclists, especially in early career females and advanced career males and females. Those low BMD values may not fully recover after the professional cycling career. Given the substantial prevalence of low BMD in retired Elite cyclists, and here’s the real kick in the bibs, an important long-term consequence of low BMD in Elite cyclists could be an increased risk of bone fractures later in life. In fact, nearly 65% of the advanced career male cyclists had low BMD at the lumbar spine, of which 50% even had osteoporotic BMD values. By the way, osteoporosis literally means porous bones. It’s why they call it the silent crippler, ’cause you really have no clue without a scan. Even recreational road cyclists face a risk, as reported in this article from C Anatomica: longtime serious cyclists do face a notable health risk, and most only realize this as a problem after they suddenly break a few bones in a minor fall. Minor. The reason for those surprising breaks? Low bone density, a common issue for avid cyclists. So, while our bone mass from the scale was in the neighborhood of the DEXA scan, the DEXA scan gives you a couple of scores that are more important. Here’s Peter AA to explain:

“There’s also a T-score, which is doing the same thing but comparing you to a young person. And so the T-score is technically used to make the diagnosis of osteopenia, osteoporosis. We tend to look more at the Z-score and basically say, ‘Look, if your Z-score right now is minus one, in four years I want your Z-score to be zero. Not necessarily because you’ve increased that entire way, but maybe you’ve increased slightly.’ While it’s expected that you would have declined, thankfully, my Z-score of 0.9 puts me in the 81st percentile. But Glenn’s Z-score of 0.2 puts them in the 58th percentile. But knowing this, your job then is to either get to zero or above, and if you’re there, you want to work to hang on to it.”

Let’s say you’ve had your DEXA, and you’ve come home, and you’ve digested the most important things from your report: your visceral fat, how much muscle you have, and your bone density. Now you have a bunch of new data. So depending on your goals—fat loss, muscle gain, bone health—it might require the right changes to your diet. So to ram back to where we began: excess weight is a biggie, and if that weight is visceral fat, then it has to go. And at the same time, we need muscle. We’re fighting age-related muscle loss. So the last thing you want to do is restrict your calories only to find out that you lost almost as much muscle as fat. Lose weight the wrong way, and you’re going to lose muscle. So what’s realistic and how can you optimize

your diet? Here’s Dr. Gabrielle Lyon, take a listen to this:

“Let’s talk about weight loss. We call it weight loss, but what we’re really looking for is fat loss. When you lose weight, typically the maximum amount of fat you could lose a week, depending on how much you have to lose, is 2 pounds a week. So anything above and beyond that is typically lean tissue, which is crazy. But if someone were to go on 100% starvation diet and lose 5 to 6 pounds a week, at least half of that would be lean tissue. And the two main ways we optimize for skeletal muscle are: number one, focusing on dietary protein, and number two, focusing on exercise.”

I didn’t realize that we need more protein as we age. For the past 24 years, I’ve been focused on low carb. But now, my head is kind of exploding. And yes, for the first time, like ever, I’m counting calories and grams of protein in our meals. And I know that sounds like a total drag, but in fact, it’s kind of fascinating. And if you’ve ever wondered, “How many calories do I burn in a day?” Well, you get your resting metabolic rate—the number of calories you’d burn if all you did was rest—from your DEXA. So, mine’s 1346 calories. Then using this table, and I’d say I’m very active, so I’m multiplying my RMR of 1346 by 1.725, and now I know if my calorie intake is under 2321 with a high protein diet, I’m likely on the road to fat loss. So diet is key to losing that visceral fat, but the other angle of attack will be exercise. And remember, the more muscle mass, the more calories burned even at rest. The more muscle, the stronger your bones. You get this from the gym. And here’s how you achieve your fat loss goals on the bike: ride in Zone Two, you know, the relatively easy endurance-building pace. So heart rate Zone Two will be a subject for a whole other video, but suffice it to say, that when we’re in Zone Two, we’re burning fat. Dr. AA recommends spending a minimum of 3 hours a week in Zone Two, and then one or two high-intensity VO2 Max workouts during the week.

And here’s some great news: I mentioned in our last video that after a full year of strength training, my muscle mass had decreased 6 pounds according to my scale, anyway. But you know how you know you get a DEXA. But how often? Well, here’s why: even if my muscle mass hasn’t improved, I may okay with that. Here’s what Peter AA said about the results:

“If you’re 50 years old and you’re in the 50th percentile, if you’re in the 30th percentile in terms of muscle mass, I’m not overly concerned, because we have a path to get you to the 80th percentile. It’s not going to happen in a year, but in 5 years, we can get you there.”

So, you’re not going to get there in a year—expectations set, thank you. And because these adaptations take time, you probably only need DEXA once, maybe twice a year. And then, gang, it starts to get super interesting, as you can see in this woman’s scans. Now you’re comparing you to you over time, and that’s so motivating. Okay, that’s it. I’ll see you next time. Let your spirit… let your spirit… let your spirit…rise.