Episode 32 - Stop wasting your money on Bioelectrical Impedance Analysis (BIA) scans

Stop wasting your money on Bioelectrical Impedance Analysis (BIA) scans 

⛔️ Don’t book in for a body composition scan until you listen to this! 

Bioelectrical Impedance Analysis (or BIA) scans are popping up in just about every gym and I’ve even seen some health professional clinics offering them as a service. 

They’re advertised as a quick and affordable way to accurately measure your body composition i.e. how much muscle, fat and bone tissue you’re made up of.

But if an athlete of mine brings me a scan to interpret, I tell them to throw it in the bin! 🙈

Listen in as I explain what the BIA scan is, how it works and the challenges with relying on this method to accurately assess your body composition.

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Episode Transcription

Episode 32 - Stop wasting your money on Bioelectrical Impedance Analysis (BIA) scans

Welcome to the Triathlon Nutrition Academy podcast, the show designed to serve you up evidence-based sports nutrition advice from the experts. Hi, I'm your host Taryn, Accredited Practicing Dietitian, Advanced Sports Dietitian, and founder of Dietitian Approved. Listen as I break down the latest evidence to give you practical, easy to digest strategies to train hard, recover faster and perform at your best. You have so much potential, and I want to help you unlock that with the power of nutrition. Let's get into it.

Taryn Richardson 0:44
Hello, hello, and welcome! How are you? Like, actually, how are you? The world is a very heavy place at the moment. And I'm not here to dwell in any negativity whatsoever. But I just want to check in and make sure that you're doing okay. If you're not okay, send me a DM on Instagram, and let's talk about it. I'm here if you do need to chat to anything. Or if there's anything, in particular, you're really struggling with at the moment. I know for me, I've really tried to not watch any commercial TV or listen to the radio over the last probably 12 to 24 months really. And that's really helped with me. Because once I'm aware of all the stuff that's going on, I really struggle to carry that burden.

Taryn Richardson 1:28
So if you're feeling a little bit overwhelmed by all the things at the moment, maybe try and tap out a little bit so that you're not getting weighed down with all the heaviness of everything that's going on at the moment and find a positive way to contribute. There are loads of things that you can do at the moment to help people in need. Here in Brisbane, we've just had some crazy flooding happening. And that's all spread down to northern New South Wales and Sydney direction now as well.

Taryn Richardson 1:53
So the whole east coast is very, very wet. There's lots of places you can donate to the flood appeal or join the Mud Army and things like that, if you do want to help out. And then further afield to Ukraine, there's lots you can do to support the people over there as well - like it is messed up! But I don't want to dwell too deep on it. I don't feel like any of that negativity needs any more air space. But I just wanted to let you know that if you're struggling and you need anything, reach out, and we'll see what we can do to support you.

Taryn Richardson 2:22
Alright, let's get into today's episode. It's a little bit nerdy, I'm not going to lie. But I want you to understand what the BIA scans are. We're keeping with our theme of body composition assessment this month. And a lot of athletes come and see me or send me through the results for their BIA scan.

Taryn Richardson 2:42
Now, BIA stands for Bioelectrical Impedance Analysis. You might have seen them in your gym, they're kind of popping up everywhere at the moment. They're those little scales that you can either stand on or hold on to or both that spit you out a report to tell you what you're made up of. They're portable, they're pretty quick, they're affordable as well - a lot of Gym Challenges will use them for before and after because it's easy. It can be done there right on site. But I want to run you through what it is and how it works so that you can understand why they're a really crap way of measuring your body composition. And to spend your hard-earned dollars tracking your body composition in other ways that are going to give you more accurate results.

Taryn Richardson 3:26
So how does a BIA scan work? So what it does is it sends an electrical current through the body. And it uses that to predict the amount of bone muscle and fat you are, what you're made up of. Now it doesn't measure directly. It uses formulas to interpret the scan and spits you out some numbers.

Taryn Richardson 3:46
So the scan looks pretty gives you a whole lot of data. And the basis is that different types of tissues in our body, they have different levels of conductivity. So when that electrical signal passes through them, it's going to spit out different results based on how easy it is for that current to move through the tissue or how hard it is. We know that lean body tissue, like our bones and our muscle, they have a higher water and electrolyte content compared to fat.

Taryn Richardson 4:15
So that means that lean tissue has a greater conductivity, which means that the electrical current passes through it easier. So we talk about electrical impedance blocking - the lower the reading of electrical impedance, the higher the lean body mass of that individual when we're talking about BIA scan results. But there are a number of challenges with this method.

Taryn Richardson 4:38
So you might have those standing scales that have the little, metal, grey silver metal, pad that you stand on. That's a type of BIA scan. It sends an electrical signal up one leg and down the other. You can also get BIA scans where you just hold on to things with both hands and then it doesn't go through the feet. And then you can also get other BIA scans, where you stand on the pads and also hold on.

Taryn Richardson 5:08
Now if you think about electricity, electrical current will always take the path of least resistance from one point to another. Think about lightning, it goes straight down to the ground the fastest way possible. It doesn't do loop de loops and zigzags - goes straight down to ground. BIA signals are the same, in that they loop from one electrical pad that you stand on to the other. So if you're just standing, then that signal goes up one leg, through the hips, straight down back through the other leg - it doesn't even loop through the upper body. The scans that you just hold on to - they send those signals in a loop from one hand, through your arm through your chest and straight back out the other hand - so it loops that top part of your body.

Taryn Richardson 5:55
Doesn't make much sense does it when we're trying to measure our total body composition? We're only doing a single loop either upper body or lower body. You get better accuracy with the four point scans, something we stand on the pads, as well as hold on to them at the exact same time, that's all linked in that same machine - that'll send that signal through your whole body. So we're getting better data with that. But for somebody that's bottom heavy, you know, holds more fat on your bottom and legs - if you do those standing ones, it'll give you a higher estimate of what your fat mass is because it's only looping through the bottom half of your body.

Taryn Richardson 6:31
Same as if you are only measuring the top half and you hold more fat down the bottom it’s going to underestimate how much fat you've got, because it's only looped through the top half of your body.

Taryn Richardson 6:43
Another challenge with these machines is - are they calibrated? Are you using the same machine when we're looking at repeating scans and repeatedly checking our body composition? Or are they swapping new machines over constantly? Are they just on higher? And, you know, how long ago were they calibrated? How many people are using it? All that sort of stuff. So a lot of gyms will hire out a machine for a challenge. It may just get brought in for that beginning scan and then taken away and then a completely different machine gets brought in for the end of the eight week challenge. So you're comparing apples with oranges if we're using totally different scans. 

Taryn Richardson 8:25
The other limitation with these scans is the estimation equations that they're using. BIA equipment uses a prediction equation developed from a different method of body composition analysis. It might be hydrostatic weighing. It might be DEXA scanning. And it's estimating your body composition based on the averages of a tested population.

Taryn Richardson 8:45
That prediction equation can become an issue for two reasons: 1. If there were inaccuracies in the original body composition measure. And 2. If the population originally tested doesn't have similar body composition to you. We could be comparing a new exerciser - someone that's new to the gym or new to triathlon - that's just getting started in the sport or just getting started with exercise, to a high performing athlete. It's like comparing apples with oranges here too.

Taryn Richardson 9:17
So depends what a prediction equation is in the back end of that as well. And the biggest reason why I think these scans suck, is that you can influence the results. Depending on how hydrated you are, how much glycogen you have stored in your muscle, or not, can completely change your BIA scan data. So take hydration for example. If you are less hydrated, the current flows slower through your bodies, there's more blocking, more impedance.

Taryn Richardson 9:47
So if you're less hydrated, then the data is going to show that you have a higher body fat percentage than you actually do - because that current’s run slower. The same with glycogen storage. When we store glycogen in our muscles, we store it with water. That water in the muscle with the glycogen helps the transport of the signal go through easier. So it makes it more conductive. So if you're glycogen depleted, maybe after a really hard training session, you've been not eating enough carbohydrate to top up your glycogen stores, or you follow a low carb high fat diet, where there's not a lot of water in the muscle, that can trick the machine into thinking you have a higher amount of fat mass than you actually do.

Taryn Richardson 10:32
So glycogen depletion means an increase in body fat percent on these scans. Crazy, hey? So you can cheat the machines, you can do a scan, drink a litre of water, do a scan, you're going to get a completely different number for your body fat percent, which sucks. We know in the literature that results can vary significantly, like up to 8% has been seen, which is just crazy.

Taryn Richardson 10:56
So if we're trying to track changes in body composition, we have really no idea what's going on with BIA scans. They'll give you a beautiful print out and tell you exactly what you're made up of. But as we've just talked about, there are so many limitations to this method of assessing body composition. And so what's the point? When we look at the research available on the validity of BIA measures, there's a huge range of results from different populations - athletic, non-athletic. Some studies see similar results to that of a DEXA, which is more of a gold standard of body composition assessment. And then others over-estimate lean mass, and also under-estimate fat mass and vice versa. All in all, that really just demonstrates a significant lack of accuracy for these scans.

Taryn Richardson 11:44
When I teach athletes what to eat for recovery, for instance, or how to calculate carb-loading, we take their lean mass to help us calculate what their needs are. So although it might seem quite harmless, when you're jumping on a scan quickly in the gym or at home, you know, it doesn't take very long and doesn't cost that much. I'd really encourage you to avoid this type of scan if you really want to accurately know what you're made up of. And also want to accurately track changes over time.

Taryn Richardson 12:15
As triathletes, we're always striving to be the best that we can be right? But with BIA scans, you are literally setting yourself a moving target. You're setting goals that might change depending on how hydrated you are, what your glycogen status is in your muscles - with results that might vary by up to 8%, which is insane. It also makes it really hard when we use things like how much lean mass you are - so how much muscle you are - to calculate things like your recovery nutrition targets and carbohydrate loading targets. It might give you a rough ballpark of where you sit, which is a good place to start. But if you really want to know how much lean muscle tissue you made up off, to calculate those things more accurately, then you're going to want to get a DEXA scan.

Taryn Richardson 13:00
And again, there is good DEXA scanning places and not so good DEXA scanning places. So if you do want to go and get that body composition assessment done, send me a message and I can direct you with the best places to go to do that. Because you don't want to just turn up to a normal scanning place, like Qscan Australia. You don't want to go somewhere like that, to get an accurate body composition scan. You want to go there to go and get an MRI or an X-ray or an ultrasound if you've hurt yourself. You don't want to get a body composition scan from somewhere like that, that doesn't do them all the time. They will offer it as a service, but they don't set you up with all the things we like to control heading into a really quality DEXA scan because, like anything, there's ways to cheat the system for that as well. And we want to turn up in a certain state.

Taryn Richardson 13:45
So what can you do instead? Throw out the BIA scans - they're waste of time, they're a waste of money. If I have a client ever bring me one, I'm like, "Oh, he can throw that in the bin, I'm not even going to look at it." Because I can't say for sure that that data on that piece of paper is anywhere close to what you are actually made up of.

Taryn Richardson 14:04
So instead of throwing your money away doing that, go and get a DEXA if you want to know legitimately how much bone you are, how much muscle you are, how much fat you are - at a place that does a quality scan. And the other option is Skin Folds.

Taryn Richardson 14:18
Now I did an episode on skin folds recently, which you need to go back and listen to if you haven't listened to that. It explains exactly what skin folds are, how we do them, and how to find somebody that's good at doing skin folds so you can get accurate data with this type of body composition assessment as well. Skin folds are great because they're affordable. They're repeatable. They're not cheatable - like they're not impacted by hydration and glycogen status and all that sort of stuff. Doesn't matter if you've eaten before or not. You can do them at any time of day.

Taryn Richardson 14:47
So if skin folds is something that you're interested in, go and listen to that episode. And then if you're in Brisbane, we do have a monthly skinfold clinic and anyone can come into that - you don't have to be a client or an Academy athlete. Just rock up. We do a 15 minute appointment, do skin folds, you get a detailed report and I'll explain to you what's going on inside your body too. But if you don't want to do any of those things - you don't want to get a DEXA, you don't want to get skin folds done - there are lots of other ways you can actually track and measure what's going on, yourself, at home, that doesn't cost anything.

Taryn Richardson 15:19
So things like progress photos, if you're into that. Your clothing size or your belt buckle size is a good one as well. A lot of men understand, you know, where that belt buckle is, like, the ultimate for them. And when they're starting to blow out. And females are pretty good at knowing when their pants feel tight and other clothes feel tight. You can also do some girth measurements yourself at home or get someone to help you with it to make sure they're lined up and nice and straight. And you can also use your weight, but just be cautious with that one, depending on what your goal is. Because it's quite a blunt measure of body composition. It's just a number.

Taryn Richardson 15:56
And if you haven't listened to the episode I did with Gary Slater on this, go back and listen to Episode 29 to learn more about why we shouldn't be using the scales as our sole method of tracking and checking our body composition.

Taryn Richardson 16:10
So I hope that's helped give you a little bit of information about why we don't rely on BIA scans for body composition. They're predicting what you're made up of based on equations that may not be best fit for you. They may not be a well calibrated machine. You may not be touching four points to send the electrical current through - if you're only doing two points then it's only measuring that loop. If it's just a stand on one, it's only measuring your lower body loop.

Taryn Richardson 16:39
If it's a just hold on one, it's only measuring your arm loop. You need it to be a four point machine. But then even then, you can cheat the system - you can be over hydrated or under hydrated and it'll affect how much body fat the machine reads. You can be fully glycogen loaded, or fully glycogen depleted, and it gives you a completely different result as well. So they're not a great measure of tracking and measuring body composition. Because it's a prediction anyway. If you want to truly know what you're made up of, go and get a DEXA. And if you don't want to radiation dose, you can't afford a DEXA, you don't have access to somewhere that is doing a really good quality scan, then skin folds is your best bet for tracking body composition over time. Because it's cheap, it's efficient, you only have to get into shorts and a sports bra, you don't have to nude up. There's no radiation dose. And we can see much more finely, what's going on with your subcutaneous fat compared to something like a DEXA, which is gross.

Taryn Richardson 17:40
You're this many kilos of muscle, you're this many kilos of fat - it'll give you a body fat percent as well. Whereas skin folds we're tracking that change to the millimetre of how much subcutaneous fat you've got at those seven body sites that we measure. So no more BIA scans! Don't waste your money. I hope I've saved you time and effort and you've enjoyed our body composition assessment theme over the last few episodes.


Taryn Richardson  18:08
Thanks for joining me for this episode of the Triathlon Nutrition Academy podcast. I would love to hear from you. If you have any questions or want to share with me what you've learned. Email me at [email protected]. You could also spread the word by leaving me a review and taking a screenshot of you listening to the show. Don't forget to tag me on social media at @dietitian.approved so I can give you a shout out too. If you want to learn more about what we do, head to dietitianapproved.com. And if you want to learn more about the Triathlon Nutrition Academy program, head to dietitianapproved.com/academy. Thanks for joining me and I look forward to helping you smash it in the fourth leg - nutrition!

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