Episode 62 - What happened when I did a Bioelectrical Impedance Analysis (BIA) scan before and after training

What happened when I did a Bioelectrical Impedance Analysis (BIA) scan before and after training

I did a BIA (Bioelectrical Impedance Analysis) scan BEFORE a 1 hour gym session and again immediately AFTER. I was inundated with requests to share what happened ... and explain why I don’t recommend these scans.

These scans are very easy to manipulate and results can vary significantly - up to an 8% variance has been seen in the literature! 

If I can gain 900g of body fat, lose 500g of muscle and gain almost a centimetre in my arm circumference in an hour - what hope do you have of your BIA scan assessing accurate change over 4 weeks?! 

There is absolutely no point in measuring something if it cannot accurately track progress. Save your $$$.


Listen to EP 32 - Stop wasting your money on Bioelectrical Impedance Analysis (BIA) scans HERE

Listen to EP 29 to learn more about DEXA scans and skin folds HERE

To book into our monthly skin fold clinic in Brisbane - Book Online HERE

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Episode Transcription

Episode 62: What Happened When I Did A Bioelectrical Impedance Analysis (BIA) Scan Before And After Training

Taryn Richardson  00:00

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  00:42

Recently, I did a bit of an experiment on myself. I did a BIA or Bioelectrical Impedance Analysis scan, right before a training session and then immediately after. And I put a call out on my Instagram stories and the response to share what happened was overwhelmingly unanimous that people definitely wanted to know. So here we are recording a podcast episode about what actually happens when you do a scan pre and post training. I'm totally happy to use my data to educate you on why these scans are not the greatest assessment of our body composition. And I did do a whole episode on BIA scans. If you haven't listened to that yet, I'd probably recommend stopping me now and going to listen to Episode 32 first. I'll link it in the description below so you can jump straight to it. But I dive much deeper into what this scan is and how it works and how they get their data, which you're probably going to need before listening to this episode because I'm going to gloss over all of those details. Once you've listened to that, come back in. And I'll tell you what happens.

Taryn Richardson  01:50

So this was definitely not planned. I did not turn up to the gym knowing that I was going to do this scan before and after. It was just there. It happened to be available. They're doing a challenge. They're using it, whatever. But I thought it would be fun. And I always have a very critical mind. And I always use myself as an experiment as well. So, you know, curiosity definitely got the better of me that day. But this was not a controlled plan thing in any way. I literally did the scan when I turned up to the gym immediately before I started training. I was actually couple of minutes late to training because I did the scan. So I wasn't fasted. I did have a milky coffee beforehand, because you know, sports dietitian, and that ticks my pre training boxes for this type of session. And I didn't control things that you could control for. Like, I didn't measure my sweat losses or urine losses or anything like that. So this is definitely not a published research study. This is just a personal experiment on myself that I'm sharing with you.

Taryn Richardson  02:53

Now some other things that do affect this scan would be my hydration status. And I would have said that, other than doing, like, actual hydration testing on the morning, I would have said that I was hydrated on waking. And I also would have said that my glycogen levels - so the carbohydrate that we store in our muscles as our fuel source, I would have said that they were normal. I'm not carb loaded. I also wasn't in a glycogen depleted state. So that shouldn't have affected results too much either. The machine was a four point contact machine scanner, not a two point which is good. And I've actually paid for the scan. It was $30. So it's not a freebie. I'm not promoting anything. I physically hand it over my cold hard cash to do this - tax deduction, but still.

Taryn Richardson  03:36

So just quickly how the BIA scan works - what it does is you hold on to the handle thing then you stand on the platform. And those little metal parts send an electrical current through your body. And they predict the amount of bone muscle and fat you are. It doesn't measure it directly, not like a DEXA scan. It uses a formula to interpret those results. And it's based on the foundation that different types of tissues in our body have different levels of conductivity. So lean body tissue, like our bone and our muscle has a higher water and electrolyte content compared to fat. And so that means that our lean tissue has a greater conductivity and that allows that electrical current to pass through easier. So the lower the reading of electrical impedance, the higher the lean body mass of the individual.

Taryn Richardson  04:29

Now on Friday, I did a lower body workout. It was a 15 minute warm up set of exercises, 30 minutes of strength where I did some, like, single leg deadlifts, I did some hamstring stuff, I did some lunges, I did some abs. And then there was a 15 minute finisher section at the end. And I'm just going to talk you through what that is because that also kind of links into what the results are. So it was a session that was one minute of max calories on the bike and then a 3 minute rest x 3. So not a lot of work - 3 minutes of hard out max sprinting on a bike, which absolutely smashes you.

Taryn Richardson  05:10

Now, I'm not diving into the physiology too deeply around what actually happens in this type of session. But the higher the intensity, the more carbohydrate we use as a fuel source. And predominantly, we draw on our muscle glycogen. But because this was one minute max, and then you've got rest, it actually teaches the body to take that lactic acid that you've just built, particularly in my quads, that actually gets converted and shunted back into glucose to use again as a fuel source in that next max effort. So I would have spared a lot of my muscle glycogen for that reason. I'm actually pretty good at reshunting lactate into glucose. It's something that I do in my training sessions. So I wouldn't have lost a lot of muscle glycogen in a strength session like this. 3 minutes of work, not a lot of muscle glycogen gone.

Taryn Richardson  05:58

I also drank about 400 mls of water through the session. See, I'm getting my sports dietitian hat on here. So I would have over drunk for my sweat losses. I'm not a very heavy sweater. There was only like three minutes of sweaty activity at the end. So I wouldn't have been dehydrated after that hour session. I would have been more hydrated than I probably started with, to be honest. So I smashed myself on the bike, did my rest, and then went and did the scan. So what actually happened?

Taryn Richardson  06:28

I'm going to put the raw numbers in the show notes so that you can see them while you're listening to me. If you're a visual person, that's going to make a lot more sense. But please don't do that if you're driving a car. So before the session, I was 61 kilos. And after the session I was 61.1 kilos. So I gained 100 grams through that session, which, I don't know, probably makes sense.  I drunk 400 mls of water that's 400 grams. It's unlikely that I lost 300 mls in sweat. But you know, whatever.

Taryn Richardson  07:00

Interestingly on the weight thing, the scan gives you like a one page report, which is honestly the most confusing thing you've ever seen in your life. And I know how to read these. There's numbers everywhere. And it doesn't explain anything about anything. But there's a little weight control section at the top right. And it says before the session, I needed to gain weight! My target weight they set at 62 kilos. And so it's telling me before I go and do training that I need to put on a kilo - like no, thank you.

Taryn Richardson 07:32

And then afterwards, it's telling me that I actually need to lose weight now. I need to lose 300 grams, and I need to lose a kilo of fat and put on .7 kilos of muscle. So the difference of an hour, it's gone from somebody telling me I need to put on weight to somebody telling me I need to lose weight. So if you didn't look at a scan like that with a critical eye, I don't know about you, but you would probably be a little bit disappointed. My skeletal muscle mass before and after - so how much, like, lean muscle tissue I had was 25.9 kilos before, and 25.4 kilos after. So it actually lost 500 grams of muscle, apparently, in my session.

Taryn Richardson 08:16

Now, I could be a little bit dehydrated, which would make sense, but I really don't think I was. And I could have lost a whole heap of muscle glycogen through that session, which again, I don't think I really did. My body fat percent - this is what most people look at first. So before, I was 23.1%, body fat, and afterwards, I was 24.6% body fat. So apparently I gained 900 grams of fat while I was in training. How disappointing is that? And they also break that down into visceral fat. Now, visceral fat is a fat that sits around your organs. I don't actually know what scale they're using. But they suggest it should be between one and nine to be healthy, because we don't want fat sitting around our organs. So it's actually really bad for us.

Taryn Richardson 09:05

So before training, my visceral fat level number was 5 and after the session, it was 6. So apparently I put on one level of visceral fat while I was training also, which would be really bad. My BMR which it would estimate from the data and use an equation - before the session was 1,383 kilocals and after the session it was 1,365 kilocals - so it actually decreased. My basal metabolic rate decreased with training. My bone mineral content also decreased with training. It went from 2.95 kilos to 2.84 kilos. Now we don't want our bone mineral content to decrease. We want them to be nice and strong, and our bone matrix to be, yeah, robust. So again, not a good change.

Taryn Richardson  09:58

Interestingly, so if we talk about the circumferences, which the scan is measuring, of like your neck, your chest, your tummy, your hips, your arms, those also changed. And now that physically can't really change in an hour session! Like maybe if you did a big bicep pump up, they'd fill up with blood. But I didn't do much upper body and my arms increased almost a centimeter. So my arm circumference's (right and left) at the beginning were 28.5 centimeters. And then afterwards, they were 29.1, and 29.2 centimeters. So just trying to highlight that these scans are not the most accurate numbers going around.

Taryn Richardson  10:39

My neck circumference also increased by a centimeter in training, and my chest also increased by half a centimeter in training. Now, everything is different. The last thing I wanted to highlight was my height. So before training, I was 169.8 centimeters. And apparently, after training, I was 168.2 centimeters. So I'd shrunk through the session. Now, that makes a little bit of sense, because when you are asleep, your spine is very relaxed, and there's no gravity and compressive forces on it. So you're actually tallest first thing in the morning, and then our spine compresses as the day goes on, and we kind of get a bit shorter, until it gets to relax and expand again when we sleep.

Taryn Richardson  11:22

So that does make a little bit of sense. But that is a pretty big shift. I really tried to stand the same way both times. But maybe I didn't. It's just a summary of this type of scan, the numbers are wildly different. And so like, what's the point of all that? Why have I just told you all of that information? It's definitely an interesting experiment. And it proves that those scans really just need to be taken with a grain of salt. They are very easy to manipulate. And you shouldn't bank on those numbers being exactly what you are or 100% accurate. Depending on your training and what you eat in the days leading up to a test, we know that results can vary significantly. Like by up to 8% has been seen in the literature. And that's in a controlled research study way. This was far from controlled.

Taryn Richardson  12:13

So to put that into perspective, if you scan yourself, and you'd reduced your body fat percentage by 4%, over time, due to the inaccuracies of the scans, you could actually read as an increase in 4% body fat. Now that is not exactly reliable, is it? And it's also very bloody disheartening. If you've worked hard on your nutrition and your training, and you get a scan, and that tells you, like mine, that hey, you've just done a training session, but you've put on fat - good work. It's not so great for our egos.

Taryn Richardson  12:46

What I should have done - would have been to go and get a DEXA first, go and get the BIA scan, like, immediately after and compare those two. And DEXA has its positives and negatives as well. Again, it's another podcast topic that I talked about a little while back. So go and have a listen to that one if you want to learn a bit more about a DEXA scan.

Taryn Richardson  13:05

But if you're trying to track your change in body composition, the best things to do - the best ways to monitor - would be, you know, gold standard is a DEXA scan maybe once a year. And then regularly doing skinfolds with an ISAK accredited anthropmetrist, every sort of four to six weeks. That's going to show you more accurately what's actually happening to your body composition. If you're using a scan like this to try and track change, it's impossible to give an accurate measure of what's actually happening. You're literally setting yourself a moving target, and you're setting goals that will change depending on your hydration status, your glycogen storage, and there could be a variance of up to 8%, which is massive. Now, I don't think there's any point in measuring something if it can't accurately track that progress. If I was really bothered with my body composition, this scan would make me feel very disappointed about the whole process of eating well and training. But because I don't care, and I know how gray these numbers are, I'm okay.

Taryn Richardson  14:15

In this case the scan is in the gym because they're using it to assess the change before and after a 4 week challenge. So if you train with me at the gym and you're listening to this and you're competing in that challenge, make sure you do a couple of things for me so that you can cheat your results and make it look like you've done an awesome job. So make sure you do your scan before you train. Make sure you're really well hydrated before you do your scan as well so that electrical conductivity is not slowed down by any extra fat and you could also try and carb load yourself as well to make sure that your muscles are full of glycogen which stores with water and helps out electrical conductivity as well. And then your first scan which is a little bit too late now. But you would have wanted to turn up really dehydrated and a little bit glycogen depleted as well, to make that scan look like you had more fat on than you actually do. But don't tell the boys, I told you to do that.

Taryn Richardson  15:14

So there you have it. A fun little experiment that I'm letting you in on. Don't do a scan before and after training just for shits and giggles like I did. It's not going to end well. And it also just highlights the gross inaccuracies with this type of scan. So save your money, go and get a DEXA scan like maybe once a year if you do want to see what's going on a bit more specifically. And then if you are trying to do some sort of nutrition intervention and drop some body fat or put on some muscle, then look for an ISAK accredited anthropometrist to do your skinfolds at regular intervals. Because you can't really cheat those. There are certain things that you can do to control them. So you want to make sure you going to the same person, you can do them at the same time of your menstrual cycle as a female, but they're not sensitive to hydration status and glycogen storage and all those sorts of things.

Taryn Richardson  16:04

I run a monthly skinfold clinic if you are local to Brisbane, otherwise head to the ISAK global website and look for somebody local in your area. The other things that you could do honestly, are do some measurements, like do some waist circumferences, hips, chest, arms, quads, calves. You could also go on how your clothes fit and feel. Sometimes we get so fixated in the numbers and the data. But you know in yourself if you're feeling good or not. Like guys, you'll know if you're on the right belt buckle where you're feeling good or not. Same as you ladies - you're very sensitive to how your clothes fit and feel.

Taryn Richardson  16:44

So just a gentle reminder that you don't need to get obsessive about this sort of stuff. If you're eating properly, you're exercising regularly, and you feel good, then maybe that's enough. As triathletes, we can get bogged down into those details a little bit too far. And I like to take the emphasis off weight and put it back on you and fueling properly because you'll feel better if you're fueling properly, instead of constantly trying to diet and starve yourself and put yourself into a calorie deficit. But fueling properly, you'll have energy and your body composition will sort itself out without you having to chase it.

Taryn Richardson  17:24

And that's something we talk a lot about inside the Triathlon Nutrition Academy. We don't talk about race weight until the 3rd Phase - once we've done a whole heap of foundational work around day to day eating and fueling training sessions. Because once you've got those foundations right, everything else slots into place so much easier.

Taryn Richardson  17:44

There you have it! Don't do a scan pre and post training - doesn't end well. If you have any questions around my scan and the data and there's something that you're not sure about, just send me a DM on Instagram @dietitian.approved or come and join me for Coffee and Questions. It's on the 1st Thursday morning of every month inside the Dietitian Approved Crew Facebook group. You've just missed this month's. But I'll see you on the 1st Thursday next month.

Taryn Richardson  18:14

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 can 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, @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 www.dietitianapproved.com/academy. Thanks for joining me and I look forward to helping you smashed in the fourth leg - nutrition! 

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