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The different methods of imaging body fat

DEXA scan body image

Knowing precisely how much body fat and muscle you have, and how both are distributed around your body, gives you a firm starting point on your journey to becoming healthier and fitter. Imaging techniques give the best information but you might be wondering which is the best method to go for when it comes to imaging body fat. What are the options?

Read on to learn about DEXA body scans, amongst other body fat measurement techniques.


Basic measuring of body fat at home


If you’d like to get an estimate of body fat percentage and do it at home, there are a couple of simple techniques to try:

  • Use a tape measure – you can use a dressmaker’s tape measure to measure the circumference of your neck and waist (for men) or neck, waist, and hips (for women). You’ll also need to know your height. Once you have your measurements, log them in this Navy body fat calculator to get a rough estimate of your body fat percentage.

  • Use skinfold calipers – another way to measure your body fat is to do a skinfold test with calipers (a popular form of anthropometry). These tools pinch different areas of your body and measure the fat percentage. There are many different formulas using a wide range of pinch-points. This body fat calculator uses the Jackson & Pollock formula, which requires testing three areas of your body: chest, abs, and thighs for men, and triceps, thigh, and just above the hip bone (suprailiac) for women.

While these methods may give you a very general and imprecise idea of your body fat percentage, for a more accurate reading your best bet is to look at body fat imaging — particularly if you want to explore your fat and muscle distribution.


Body fat imaging


Body fat imaging, using expensive medical-grade technologies, gives you a precise measurement of your fat percentage as well as a visual image of where it sits around your body. Imaging is much more accurate than tape measures and skinfold calipers because it is not subject to human error (which is a huge volatility factor with calipers) and is not affected by hydration levels in the same way as bio-impedance tools are. Imaging provides much more comprehensive data, giving you (with the help of a proper interpretation) a detailed insight into your body composition.


MRI or CT scans


Magnetic resonance imaging (MRI) or computerised tomography (CT) scans are two of the most accurate ways of imaging body fat. They work by taking cross-sectional images of the body thanks to the machines’ circular ‘doughnut’ design.

However, while MRI and CT scans offer accurate results, they are very rarely used for just measuring body fat. They are very expensive pieces of machinery (with scan prices to match!) and were designed to detect serious medical conditions such as brain tumours and calcified arteries.

A CT scan exposes you to extremely high doses of ionising radiation (X-rays) so exposure would not normally be justified simply to measure body fat (which would require total body exposure).

MRI uses radio waves, not X-rays, and also produces a 3D-like image by stitching its cross-sectional images together. Like CT, MRI is a ‘big gun’ in the imaging arsenal and used primarily for serious medical conditions such as cancers, liver disease, tumours, vascular conditions and heart problems. As a result, it is expensive to access, and it’s very unlikely that you will find anyone to interpret an MRI scan in terms of body composition. MRI practitioners and radiologists will be specialists in disciplines like oncology, urology and neurology. (A similar example is that most GPs know very little about nutrition, which is bizarre considering more than two-thirds of the UK population is overweight or obese!)

If you’re interested in using an imaging technology to accurately measure your body fat percentage to help with your health and fitness goals the most suitable option is a DEXA body scan.


What is a DEXA scan or ‘DXA scan’ (Dual-energy X-Ray Absorptiometry, sometimes mispronounced ‘Dexter scan’)?


A DEXA body scan uses an extremely small, very safe dose of X-rays to measure your fat, lean muscle, and bone. These scans present the information in a report that gives you a clear, detailed picture of your body composition.

In contrast to MRI and CT scans, DEXA scans are much quicker, cheaper and more accessible, and they do not present the frequent challenge of claustrophobia caused by being inside the ‘doughnut’ ring. The scanning arm of a DEXA scanner always stays at least 30cm from your body.

As well as accurately and precisely measuring your body fat and lean mass, a DEXA body scan also gives a good indication of your bone density. However, this is not accurate enough to make a medical diagnosis and, if you have concerns about bone density or osteoporosis, speak to your doctor to arrange a DEXA scan specifically for your bones, and watch this video or read this for more information


Why get a DEXA scan?

Like CT and MRI, DEXA is a high-end medical-grade technology, but in contrast to those multi-disciplined technologies, DEXA is only used for measuring two things – bone density or body composition.

This means that a DEXA provider like Bodyscan will be an expert in its chosen modality. In Bodyscan’s case, this means we are experts in all things body composition and can interpret your results in detail and in plain English. As of Spring 2022, we have performed over 17,000 body scans and have built the largest DEXA dataset in the UK and, we believe, Europe.

Having a detailed picture of your body composition will enable us to set specific targets for fat loss, muscle gain or both. With our unrivalled experience, Bodyscan’s consultants can suggest exactly how much body fat you could lose, how many calories you should eat and how long it will take to reach your goal. Our experience with DEXA means we can make sense of every number on your report and will go much, much further than just giving you your body fat percentage (which is not a very good measure of fat anyway, as we explain here.)

A DEXA scan from Bodyscan will also assess your risk from internal visceral fat and advise you how to adjust your exercise and diet to minimise the risk from obesity-related diseases, such as type-2 diabetes, with which visceral fat is associated. (Immediate tip – increase your level of activity to start reducing internal fat.)

Because a DEXA scan is extremely consistent and reliable between scans, follow-up Progress scans will accurately measures even very small changes in body fat, so it’s a great resource for tracking your progress. Regular scans can help you see which areas need more focus, keep you motivated and provide the evidence to stop doing stuff that simply isn’t working. We can also help you develop a tailored nutrition plan to help you reach your target weight or body fat percentage.

Whether you’re looking to lose fat or gain muscle, a DEXA body scan is a great place to start. Book yours today! Details of our two London clinics are on our Contact Page.