Laboratory Body Composition Tests to Measure Body Fat Percentage

Summary

In this informative video, Evan Matthews delves into various laboratory methods used to measure body fat percentage, discussing their pros and cons. He touches on popular techniques like Dual Energy X-ray Absorptiometry (DEXA), Hydrostatic Weighing, and Bod Pod Air Displacement Plethysmography. The video offers insight into why DEXA is considered the gold standard despite its high costs and radiation concerns and explains how Hydrostatic Weighing and Air Displacement methods work, detailing their intricacies and limitations. Matthews also highlights the nuisances of field vs. lab-based body fat assessment methods, ultimately guiding viewers to choose the best method for specific circumstances.

Highlights

• DEXA provides comprehensive insights into bone, lean tissue, and fat mass but involves high costs and radiation 📊.
• Hydrostatic Weighing, once a gold standard, measures body density through water displacement, but factors like lung volume can affect accuracy 🌊.
• The Bod Pod offers an air displacement method that is less intrusive than water, though it requires shaving body hair for accuracy and is expensive 💨.
• Different states have varying regulations on using DEXA due to its use of radiation, which can impact accessibility 🚦.
• Despite the advantages of lab-based methods, field-based techniques offer a practical solution for gyms and less-equipped facilities 🏋️.

Key Takeaways

• DEXA is the gold standard for body fat measurement, providing detailed body composition insights but it's pricey and involves radiation ⚖️.
• Hydrostatic Weighing uses underwater displacement to determine body density, a method that's precise but not always comfortable for users 🌊.
• Air Displacement Plethysmography, such as the Bod Pod, offers a dry alternative to underwater weighing, yet it is still costly and requires minimal clothing 🎈.
• Each method has its pros and cons, so the choice depends on resources and specific needs in research or clinical settings 🔍.
• High-end facilities and research centers typically have access to lab-based body fat measurement techniques, unlike common gym settings 🏥.

Overview

In this video by Evan Matthews, the spotlight is on how different laboratory methods are employed to gauge body fat percentage, weighing their advantages and disadvantages. These methods, including DEXA, Hydrostatic Weighing, and Bod Pod Air Displacement Plethysmography, each have unique attributes that make them suitable for various purposes.

The DEXA scan stands out as a gold standard in body composition analysis due to its high precision and capacity to offer detailed insights into bone, lean tissue, and fat mass. However, its cost and the involvement of low-dose radiation, which is subject to stringent regulations in some areas, often limits its use to clinical and high-end research facilities.

Meanwhile, Hydrostatic Weighing relies on underwater mass evaluation to calculate body density, offering accurate results but posing inconvenience due to its need for participants to be submerged entirely during the process. Bod Pod presents a less intrusive option, using air displacement in a pod-like structure, though it demands shaving of body hair and is less accessible due to its high cost. Matthews concludes by hinting at more accessible field-based techniques discussed in another video, bridging the gap for common gym-goers.

Chapters

• 00:00 - 00:30: Introduction to Body Fat Assessment Techniques The chapter introduces various techniques for assessing body fat percentage, emphasizing their pros and cons. It aims to help readers choose appropriate methods for different situations. The chapter mentions that some methods like MRI and ultrasound are not covered.
• 00:30 - 01:00: Common Body Composition Assessment Methods In this chapter, various methods for assessing body composition are discussed, with a focus on 3D scanning techniques. The chapter identifies dual-energy X-ray absorptiometry (DEXA) as the current gold standard for body composition analysis. Although magnetic resonance imaging (MRI) might offer comparable or superior assessment capabilities, it is seldom used outside of research due to its high cost.
• 01:00 - 02:00: DEXA: The Gold Standard The chapter titled 'DEXA: The Gold Standard' explains how DEXA is utilized primarily in clinical and research environments, serving as a benchmark for comparing results from other methods. It highlights DEXA's capabilities to assess not only body fat percentage but also lean tissue, bone, mineral content, and fat mass. DEXA was considered the gold standard before methods like hydrostatic or underwater weighing gained prominence.
• 02:00 - 04:00: Hydrostatic Weighing The chapter discusses the method of hydrostatic weighing as a technique for measuring body composition. Although once common, it has been overshadowed by more modern methods such as DEXA and air displacement plethysmography. The latter is exemplified by the Bod Pod system, which is prevalent in high-end and academic research facilities. These various methods offer different approaches to assessing body composition.
• 04:00 - 06:30: Air Displacement Plethysmography (Bod Pod) The chapter discusses the concept of calculating body density and body fat. It highlights that skinfold measurements, which will be discussed later, are used to assess body density. From body density, body fat can be computed using various equations, including the Siri equation. These methods are not direct measurements of body fat or density but are used as assessment tools.
• 12:30 - 13:00: Conclusion and Upcoming Video This chapter discusses different methods to measure body fat and water content. It begins with a description of subcutaneous fat measurement through pinching. Then, it introduces Biological Impedance Analysis (BIA) as a common method for determining body fat percentage and estimating body water. The chapter notes that some measurements are typically used in field or gym settings, while others are more specialized.

Laboratory Body Composition Tests to Measure Body Fat Percentage Transcription

• 00:00 - 00:30 all right let's switch gears now and start talking about how people assess body fat percentage we're not going to show how to do each one of these but we're going to talk about the pros and cons quickly of each one so you can determine which one may be a good one to use in different situations all right so this is a list of some of the most common methods of doing body fat assessment or body composition assessment there are certainly other ones out there a lot that i'm not showing on here like uh mri ultrasound
• 00:30 - 01:00 various 3d scans of the body there's a lot of them this is something that is consistently getting new techniques developed but again these are the common ones so dual energy x-ray absorption geometry or dexa that is probably the current gold standard for this um excluding mri which is probably as good if not a little bit better than the dexa but it's not used outside of research settings often because it's so expensive even dexa
• 01:00 - 01:30 is typically only used in clinical or recent research settings which is why it's it's useful as a gold standard to compare the results of some of these other ones too but it's it's good for assessing body fat percentage of course but also lean tissue because it can see the lean tissue it can see bone it can see mineral it can see fat mass next one on the list hydrostatic or underwater wing this was the gold standard for a very long time
• 01:30 - 02:00 underwater wing is still a good measurement it's not used as frequently as it used to because it's been sort of surpassed by dexa and also the next one on this list here which is air displacement platfismography um the only system i'm aware of for air displacement plus esmography is the bod pod system it's it's fairly common in your high-end facilities and your academic and research facilities both of these measurements as well as
• 02:00 - 02:30 the skinfold measurement that we're going to talk about in a second are we going to calculate body density and from body density you can calculate body fat using an equation similar to the series equation i have listed here but there are other equations that will also go from body density to body fat so these are not actually body fat measurements or body density measurements but again we typically use them to assess body fat all right so the next one is already quickly mentioned with skin folds
• 02:30 - 03:00 measuring the subcutaneous fat under the skin by pinching the person and then biological impedance analysis or bia um is another one that that's uh commonly done and it it's going to determine um how much fat the person has also it's very useful for estimating how much body water the person has and these two down here are your typical field or gym based measurements where these ones up here are usually only going to be seen in very
• 03:00 - 03:30 high end facilities or research or clinical settings but we're going to talk about each one of these in a little more detail so dexa here the dual energy x-ray absorption you can see an image that you would get from dexa machine you can see the skeleton this was originally used only for or maybe not only for but it was originally designed in order to measure bone density and it's still used for this all the time in clinical settings but as you can see in the second picture
• 03:30 - 04:00 you can also look at tissues and so your soft tissues and so you based on the sort of density of the the coloring here you can sort of pick out fats versus lean tissues and you can even see the lungs in here and so it's useful for looking at soft tissues as well and this is what a typical dexa machine looks like and it's got this one that's going to sort of scan over the person or a specific segment of the person using x-ray type waves
• 04:00 - 04:30 and so again you can get all kinds of different measurements from this this is just a short segment of what you can get some of the pros for this again it quantifies bone as well as the soft tissues so it can give you a measure of bone density which is health for health reasons is is very useful which clinically is probably more common to use dexa for that rather than body fat percentage highly precise highly reliable which is why it is that gold standard and i had
• 04:30 - 05:00 it with the three different stars on the in the previous slide uh some cons to dexa very very expensive so these machines are probably going to be starting somewhere around thirty five thousand dollars a piece and they can go up into you know well over a hundred two hundred thousand dollars if you want sophisticated measurements from them another issue with dexa is it does use a low dose of radiation it is based on x-rays which
• 05:00 - 05:30 gives radiation so some states are going to make it very difficult to use a dexa machine others will not currently new jersey which is where i'm at at the moment is a state that highly regulates dexa and you need to have a special education and license in order to run a dexa machine if i go over the border into pennsylvania the rules are much more liberal there
• 05:30 - 06:00 about dexa machines and basically anybody can learn how to use in a few minutes and then use it on people so it's much more commonly used in states like that because of the the looser regulations um i don't know the exact numbers here but when i've talked to people from companies that make these uh types of machines that keep in mind it's coming from someone who sells the equipment but i've been told that the dose of radiation would be equivalent to eating like a you know four bananas or
• 06:00 - 06:30 something like that because bananas have potassium that has a radioactive component to it so we're talking about a very very low dose of radiation in most dexa machines and so it's probably not a big concern but again some governmental bodies have decided to regulate it pretty tightly so it's not as easily accessible in some states as others here's our underwater wing or hydrostatic wing for this you'd weigh
• 06:30 - 07:00 the person on dry land you'd have to assess their how much volumes in their lungs because you're always going to have a little bit of trapped air that has to be uh taken into account um here and then you put them under water and you weigh what uh weigh them under the water you so you see the difference in their weight on dry land versus wetland or underwater and from that we're able to calculate body density it's basically a displacement measurement because you're displacing water and how much water you displace is going
• 07:00 - 07:30 to determine your buoyancy in the water so sort of basic understanding here muscle is heavier than water fat is lighter than water so if you have more body fat you're going to float more you're going to look lighter under water than if you have less body fat or more muscle mass you will you would sink more that's the very basics of this so some of the limitations of hydrostatic weighing is it does have the confounding effect
• 07:30 - 08:00 of air volume that's in your lungs because air also causes buoyancy and causes you to float uh which is why when you go under the water you have to blow out as much air as you can but you still have residual volume of air in your lungs that you can't get out it's always trapped in your lungs that's normal it's part of normal healthy pulmonary physiology so there's always a little bit of air trapped which is why you need to either measure the residual volume of the person or estimate it through some form of uh
• 08:00 - 08:30 voluntary uh expiratory capacity test some other pretty obvious limitations hopefully that aren't listed here is that you are being forced to go underwater so you're um you're getting wet you're typically wearing a bathing suit so that might make some people uncomfortable when you're under the water you're blowing out all your air a lot of people do start to get a little claustrophobic because the tanks tend to be pretty small as you can see here
• 08:30 - 09:00 and they kind of need to be to keep the water stable and not have it sort of bouncing around making waves that make it hard to read the weights so all those things can be things that make some people nervous when they're having this test done and might make it unpleasant for them all right so uh this as i already mentioned is a hydro of the hydrostatic weighing test is a body density test not a body fat percentage test and so i have it listed here as a limitation because you
• 09:00 - 09:30 have to do a conversion for body density body fat which isn't a big deal it's pretty easy you know it's like a couple step or equation or something like that um but everybody's body density is a little different so if you assume a certain body density for a person and you end up being wrong it can lead to errors in the body fat percentage calculation this is going to be an issue with any of the body density based body fat assessment measurements so it's not
• 09:30 - 10:00 just this one that has the issue all right so again fat free density does vary amongst different people on to air displacement plasmography again bod pod is the only method of this that i'm aware of if you know of another machine out there that does this i would love to know about it so you know put a comment below so i can i can learn about it but bod pods are fairly common they
• 10:00 - 10:30 they're in a lot of high-end fitness facilities and athletic facilities and they're in a lot of research and academic institutions this is the bod pod you can see it's got this sort of egg shape to it it uses similar concepts as underwater wing but instead of displacing water and measuring your buoyancy you're displacing air and there's a sort of bladder behind him there's behind this wall here that's
• 10:30 - 11:00 going to be able to assess the volume of the air that you're displacing um and so um it's got those same issues with you know your measuring body density here again and the various issues associated with uh going from body density to body fat percentage uh it is much easier for these the participants than underwater wing because they don't need to get wet they don't have to blow out all their air you do have to assess air volume in some
• 11:00 - 11:30 way in their lungs the volume or do some sort of general prediction equation which is probably more common but it is much easier on the person than underwater weighing is um so um there's that benefit some of the negative sides though is you do have to wear minimal clothes and you really should cover or shave off
• 11:30 - 12:00 any hair that is exposed because anything that traps air is going to actually increase the error of the test so notice he has a cap on his head uh compressing his hair um he should have his hair on his chest shaved we didn't in this case but typically you should especially if it's like a clinical research measurement where you need a lot of accuracy to it you can't see it but he's wearing compression shorts obviously he has a
• 12:00 - 12:30 shirt off so women would have some sort of sports bra or bathing suit on while doing this similar to what would be done with the underwater weighing also fairly expensive these machines are going to cost you somewhere between probably 50 and 55 thousand dollars to buy so not something that your typical general fitness facility is going to be able to afford so we've talked a lot about different methods of doing body fat percentage assessment but up until now all the techniques i've talked about or lab based techniques
• 12:30 - 13:00 i'm going to put a link in the description of this video to another video where i talk about field based techniques