Body Composition 101: Advanced Methods to Measure Body Fat and Lean Mass – Part 3

20 Minute Fitness Podcast #005

Welcome to Part 3 of our Body Composition Series! Jump to Part 1Part 2 ・Part 3 ・Part 4

Learn about what to measure and track our body composition. This episode marks part 3 of our body composition series in which we teach the basics of body composition, what to measure, how to measure and track and set the right goals.

Part 3 compares various advanced methods to measure ones lean mass & body fat. Methods include hydrostatic weight, 3D body scanning & DEXA bone density measures. By the end of this series, you’ll be able to make better choices in exercise and nutrition to get into perfect shape.

Show Notes

Last week we looked at how a skin caliper can measure your body fat % by pinching your subcutaneous fat (fat directly under your skin) and we looked at how we could use a tape measure to track changes to your muscle girths. However, if you tuned in last week, you will quickly have found out that these methods of body composition analysis do have their flaws.

This week we want to discuss a few more methods of recording your body data, including ShapeScale, BodPod, Hydrostatic Weighing and more.

The majority of these methods do provide more reliable and accurate results but, of course, they all have some disadvantages as well.

It is all well and good understanding our body composition and how to track and measure progress but how do we know where we should start? Should we look to reduce fat or gain lean mass?

You will have to wait until next week to find out!



Hello and welcome back to another episode of the 20 minutes fitness podcast. This is episode number 4 and it marks the third edition of our body composition series. I want to say that I hope you’ve enjoyed listening so far and I want to welcome back those that have joined us since the start of our podcast journey.

So let’s briefly recap last week’s episode. Last week we explored how to track any changes in body composition using methods such as skin calipers and basic tape measures and your traditional bathroom scales or even a Wi-Fi or smart scale and it became apparent that although these methods are cheap and accessible and they can to some extent help you measure your progress there are a lot of inaccuracies associated with them.

We explored all of those last week and so this week we’ll be moving on to more accurate body composition analyzers. We’ll be looking at hydrostatic weighing the water dunking test, DEXA scans, ShapeScale, Bodpods and Inbody devices and if we have time we’ll also be looking at how you can monitor your progress visually using things like mirrors and body composition charts and so on, so let’s get into the show.

Hydrostatic weighing or Hydrodensitometry takes the subjects density reading, it is based on Archimedes principle of displacement and this states that a body’s underwater weight is directly proportional to the volume it displaces. The dunk measures your underwater weight which is then used to compute your body’s volume. So how exactly does it work?

First of all you’ll take your dry weight, this is the weight you are usually on land and you’ll want to do this in the minimal clothing as possible for the most accurate reading.

The individual is then positioned on a specialized seat or platform and they’re instructed to exhale as much air as possible. This because your residual volume (the amount of air left in your lungs after you exhale) is part of the
body density equation, which is your weight in dry mass minus minus the weight in the water divided by density in water minus your residual volume. This will be repeated three times. You’ll be dunked underwater and exhale as much air as possible because you want as accurate an air residual volume reading as possible. There is some slight discomfort with this as you really have to force yourself to stay underwater. It’s not natural to exhale underwater but the results do speak for themselves, it is an accurate method of measuring your body composition. They then use the Siri equation to calculate your body fat percentage.

So what are the various advantages and disadvantages of hydrostatic weighing? Well obviously the
first one is greater accuracy. In fact, it was actually known at one point or thought at one point that hydrostatic weighing was the gold standard of body composition analysis. The margin of error is plus or minus 2.3 to 2.8 percent and so
you are really getting quite an accurate reading of your body doing this method.

However there are disadvantages. It’s expensive. Taking one test alone can be anywhere from fifty to seventy dollars so it’s not really a viable method to track your composition. Perhaps you could do it once per month but it’s not viable to do it more frequently than that. It’s also a question of accessibility. I know when Team Shape were trying to go for our hydrostatic weighing test we had to travel about an hour to find the nearest place that would take it. So you know, if you have a busy schedule or if you don’t really want to travel that far to take your body composition test every
time you want, you might want to think again, it might not be the right solution for you. We’ve already mentioned the discomfort and also certain demographics won’t actually be able to use this test. For example, if you’re a cardiac patient or you’re very senile or severely overweight and again you have to obviously you have to book an appointment so it doesn’t necessarily fit around your schedule.

We then looked into the bod pod which is another way to estimate the body’s volume but it uses air pressure and the way this works is with two distinct chambers, one with a seat where the individual will be sitting known as the test chamber and there’s a separate section known as the reference chamber and so the pod is designed so the chamber allows air to flow in a very specific way so when pressure increases inside the test chamber it decreases by that exact amount in the reference chamber. So in order to estimate the body’s volume air pressure is measured in both chambers without the body present and then when the body is present. It is taken again and the difference between these two is the volume of the body. So much like the hydrostatic weighing test, the advantages and disadvantages are really quite similar. The advantages are it is quick and accurate measurement again, about plus or minus 2.3 to
2.8 percent but the cost is around $45 per test and you will not be able to find many facilities nearby your location that actually offer these tests.

Moving on to the gold standard of body composition analysis. DEXA scans have replaced hydrostatic weighing and Bodpods as the gold standard. They use a three compartment model to analyze your body composition and if you think back to two podcasts ago, body composition 101 we looked at body composition in a two compartment model. This considers fat and fat free mass, the DEXA scan uses a three compartment model and separates your body according to your lean mass, your body fat mass and your bone mass. Dexafit are very well known for taking DEXA scans for individuals and they state that
it is really important knowing your bone mass because it helps you understand your risk of osteoporosis and other low bone mass issues, so DEXA scans can show you your lean mass and body fat distribution. They can
actually show you how much mass you have on one arm compared to the other, how much muscle you have on one arm compared to the other arm for example and this is particularly interesting as you can gain an understanding as to whether you’re potentially overloading one muscle while training more than the other. So if you are,
let’s say for an example squatting and you’re DEXA scan is consistently showing you’ve got more muscle mass on your left leg than your right leg, potentially, you’re exerting more force and driving up with more force than your left leg so you’re
actually overloading and stimulating the muscle more there. So it might actually help you to go back and fix your form and get a better muscle balance.

So how do DEXA scans work? So you do really need to know a bit about X-rays
to understand how a DEXA scan works, but basically the scan exposes patients to x-rays of differing intensities and they measure the absorption of each beam into different parts of the body and so there’s different readings developed for bone mineral density, lean mass and fat mass and as I’ve previously said the advantages are that it is the method to
use for the most accurate body composition analysis with a margin of error of around plus or minus 1 to 2.5
percent and obviously you’re getting localized readings rather than just an overall figure, so you have that greater data presentation of whether you have more muscle or more fat in your left arm compared to your right.

The disadvantages to expect to have the most accurate method measure you are that it is the most
expensive. So one scan alone can cost you a hundred and fifty dollars so again if cash flow is tight then you will not be
able to use the DEXA scan consistently to track your body composition. This is perhaps more suited to people that are only testing their composition for a show or something like that. They’re not easily accessible, when we went to get our own scan again we have to drive about 50 to 60 minutes and it’s appointment only, so it does not necessarily fit around your schedule. But that’s the price you have to pay for added accuracy I suppose!

Moving on to the Inbody and the Tanita scales. These are very popular in many gyms and sort of nutrition shops and things like that. We briefly spoke about how they work like digital smart scales using bioimpedance and if we just briefly recap.. so usually they have two sensors, one for your hands and one for your feet and they measure how quickly electrical impulses return. This is because the different speed of return gives you data to put into an equation, which derives a figure for your body fat percentage. So the signal passes through water and your hydrated muscle tissue but it hits resistance when it reaches a fat tissue (the resistance is known as impedance hence the name). The leaner you are, the faster the response time of the electrical impulses.

So one of the problems with bioimpedance and the reason why do we not rave about them and this is really because when we train we are adapting not only our adipose tissue but our skeletal mass as well and as we talked about in body composition 101 your skeletal muscle mass is 60 to 80 percent water and if the electrical impulses from bioimpedance are traveling through the hydrated muscle tissue and the hydration of the muscle tissue changes throughout the day (because we lose three point one two kilograms of water in a day) then you can really get to see the picture that your results will fluctuate depending on how hydrated you are, what you’ve eaten and the plethora of reasons like that.

But the advantages are…they’re quite accessible actually . I mean a lot of nutrition shops and gyms have the the
Inbody scales as they are too expensive to buy really for personal use (they can cost over ten thousand dollars). But they dollars but they have quick measurement time you don’t really need any assistance, it’s very simple to use. There are affordable handheld versions of such bioimpedance body composition analyzers such as the Omron, if you want to look those up. Many of themanufacturers for the different bioimpedance analyzers quote an accuracy of plus or minus 2 percent, but as I’ve said the readings can be affected by hydration levels depending on when you’ve eaten and how hydrated you are throughout the day. They can also be affected by your skin temperature, your skin moisture, the room temperature and a whole host of reasons.

Moving on to the most important one…. ShapeScale. So like hydrostatic weigh and Bodpods, ShapeScale uses algorithms similar to them which involves density, weight and volume. So how does ShapeScale work? Well, what happens is that you step on and the RGB and depth-sensor will rotate around your body, I’m sure you’ve seen the robotic arm looking thing in one of our adverts or on YouTube or something like that and this will capture your body data and this scan will take no longer than 60 seconds and it will sync automatically with the ShapeScale App. The depth-sensor is actually projecting infrared coded light onto your body to catch the depth of close to 15 million points every second and don’t worry this is
radiation-free, there’s no harmful radiation here and then the point cloud that is captured from the RGB and depth-sensor is then converted into a accurate 3D body model and the photos are then sliced and stitched to create a sort of
photorealistic texture. This is one of the overriding benefits of ShapeScale rather than other conventional 3D scanners, you get that real detail USING ShapeScale, you get to see skin color, texture, everything. In others, you just get a gray shell of your body, ShapeScale is a more personal experience, you can really become motivated by your results because what you are seeing in your avatar is yourself, your body, not just an outline of your body. If you’re interested in finding out more reasons as to why ShapeScale is different from other 3D conventional scanners, then you check the support page on our website and you can look into that .Just literally type in how ShapeScale differs to other 3D scanners.

I can briefly outline them to you. So ShapeScale is more portable, it’s about ten pounds, so five kilograms or so and it’s one component whilst others are two different components. With ShapeS cale the human body is not being rotated, rather the robotic arm is rotating around the body and this minimizes micro-movements that occur as when someone is being rotated they often move, their body posture changes and if the human is stationary this inaccuracy is minimized. There are a few more differences between shape scale and other 3D scanners on our website. So I think I’ve said some of the benefits but let’s go into more advantages of ShapeScale. We really do think it’s the future as it is the best of both worlds because it is calculating your body fat and as well as giving you visual data so you can see yourself and it’s also giving your muscle growth measurement so it’s combining a lot of the things we’ve already talked about into one. The sensor is actually accurate to less than 1/16 of an inch which is very precise data. There’s all sorts of amazing features like the heat mapping technology that allows you to visualize areas of your body and see where you’ve been gaining muscle and losing fat and this is possible because muscle and fat has different densities. The scans allow you to visualize your progress that you wouldn’t normally see with the naked eye.

Because the scan is so precise you can use ShapeScale more frequentl, so you constantly get that reassurance that you are
progressing rather than reaching that period when you feel you haven’t made any changes to your body by simply looking in the mirror and it starts to demotivate you. Using ShapeScale you’ll constantly know whether your training is paying off or whether you need to mix things up and obviously it’s free from any distortions. When you’re
using a mirror all sorts of things make a difference to what you see, such as the lighting, even your own head! You can
actually manipulate what your thoughts are of your own body are because the subjective factor comes into it. Finally ShapeScale becomes more accurate the more data that’s collected, because in the server’s ShapeScale is processing and making adjustments to account for discrepancies in posture and bloating and things like that.

So obviously, I have to mention some disadvantages as well. One of them being, it’s not quite as accurate as DEXA scans which we’ve already covered as they have a three compartment model. Many people may find that the initial instalment cost for ShapeScale is expensive but all I can say to this is that you know it’s a revolutionary new bit of technology that will really help you reach your goals more effectively and more efficiently, as it combines many of the different components of earlier mentioned body composition analyzers into one model or one body composition method and
so it really will be worth the initial outlay.

We were going to talk about other ways you can visually track your progress, but I don’t think we have that much time left. Obviously, the different methods we can quickly just mention are using a mirror. As I’ve already said there’s all sorts of things like the lighting, the way you see yourself etc.that distort your progress perception. You could use progress pictures but again these can differ depending on the lighting, the time of day you take them and all sorts. Obviously,
do not get fooled by a lot of transformation photos you see on social media because they are quite often touched up. We’ve done a whole blog piece on that as well. You can also use these body composition charts which I wouldn’t recommend doing. They sort of compare your body to average body fat percentages and you know everyone’s body is different so that’s really not the the method I would tell you to use. There are a number of apps as well, if you read the ultimate tracking guide we mention a number of apps you could use to track your progression visually. Such as Snapsie a transformation photo sort of app.

Yeah that’s about the extent of it so I think we’re gonna have to sign off now! Thank you very much for listening and I really hope you’re enjoying the body composition series.Next week we will be talking about goal-setting and how to know whether you should try and gain lean mass or lose body fat first. What should you do with your body first in terms of goals. Please head over to Itunes or stitcher or Google Play and leave as a review. I’d love to know how we’re doing and if you have any topics you’d love us to cover. Please write a know a comment on that because we’d be happy to to cover anything that people are interested in.

Thank you very much for listening this has been the 20 minute fitness podcast with Charlie.

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You have listened to Part 3 of our Body Composition Series! Jump to Part 1Part 2Part 4

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Charlie Farmer

Charlie is content writer and community manager at Shape.
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