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Why is Body Composition Important?

by | Dec 14, 2019 | DEXA, Fitness Lifestyle, Fitness Science, Nutritional Science, Science

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This post discusses why, if you haven’t already, you should change from using only your bathroom scales to measure your progress in the gym, to using Body Composition.
For some it’s a morning ritual – get up, stand on the scales, then feel great, or worried, or indifferent to the result between your big toes. Make no mistake: regular checks of your weight can tell you exactly that – whether there’s been movement up or down. Of course, we  have to allow for daily fluctuations. A small dinner or being dehydrated can send the figures down a bit, while a large or salty meal the night before can send the figures up by a kilo or so.

Over time, it is the movement in weight – the general trend – which counts. But what is this figure telling you? Sure, you might be heavier but we don’t know that it’s all fat. As noted above, you might just be holding on to a bit of water. Sure, you might be lighter, but if you’re 3 days into your Ketogenic diet, then you body is going to release a whole lot of water, and you could suddenly show up 3 kilos lighter. .

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Then, and what really throws a complicator in, is the effects of exercise. What if the extra weight is a little more muscle – if you’ve been working hard on your weight training? What is the extra weight is an increase blood volume, if you’ve been working on your aerobic fitness. None of this detail will be shown by your scales.
Further, when we are losing weight, we lose from all our body’s tissues. From lean mass, from fat, and from bone. What if your body is losing disproportionately from one of these?
All these factors surrounding exercise are a great reason to move away from the scales as your only source of information on your progress, but to try to gain a deeper understanding of what is happening to your body composition. That means trying to assess what your body is currently made of.

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There are many ways to measure Body Composition. From the simple and low-tech such as skin fold callipers, to the extremely high tech methods like hydrostatic weighing, the Bod Pod – air displacement, and DEXA Scanning.
To a greater or lesser degree however, they are all aiming at moving beyond the total weight figure, and getting a breakdown of that into a percentage of body fat.
With this one bit of information, you already have a far greater understanding of what your efforts at the gym or on your diet are producing. An increase of weight, but reduction in body fat percentage means (for most people’s goals) you are doing really well!  You have increased the amount of muscle or blood relative to the amount of fat. A decrease of weight, and decrease in body fat percentage would mean that you are losing fat faster than you are losing muscle. Once again, for most people’s goals that would be great news.
If however you are losing weight, but your body fat is increasing, this might mean that you are disproportionately losing muscle – this should be avoided at all costs. Your diet may not be right – or you might be cutting too deeply from your suggested number of calories. Similarly an increase of weight and increase in body fat may mean that you are eating too much relative to the intensity of your workouts. 
Of course the above are just examples of what might be happening – individual results will vary, and some combination of factors may be at play. 
Body fat percentage also helps you to more accurately judge your calorie requirement. As fat is ‘passive’ tissue – i.e. it doesn’t consume calories to maintain, while muscle is ‘active’ tissue, meaning that it does consume calories to maintain – it is important to understand how much of each you have in order to better gauge your caloric needs. 

While we are on the subject, it is worth touching briefly on Body Mass Index. Most of you will know this, as this is the method still used by GPs to assess patients and categories them into ’underweight’, ’normal range’, ‘overweight’, and ‘obese’. BMI is just your weight (in kg) divided by your height (in meters). 
BMI is a terrible equation to use for anyone who has ever set foot in a gym. The only reason it is still used is that it is quick, doesn’t require any skill or equipment other than scales and a height ruler on the door. It can be reliably carried out by GPs who naturally want to focus on acute conditions rather  than refining their skills with a skin fold calliper. We have to also remember that here in the UK, only 17% of people have a gym membership, so for many people, like scales, it might be a valid measure. However, put any CrossFit Athlete, or body builder through the equation, and they are almost certain to be assessed at some level of ‘overweight’ or ‘obese’
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“here in the UK, only 17% of people have a gym membership”

Source: IBISWorld report on Gyms and Fitness Centres UK

So, by all means continue to use the scales, but upgrade your understanding of the changes happening to you by one of the more precise methods of body composition analysis. My Vital Metrics offers DEXA scanning as the gold standard. You can get more information about DEXA here. Look out for our upcoming smackdown between DEXA and other body composition methods.

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