A 3min Read
Body fat monitors & body composition testing has become very popular in recent years, whether it’s a bathroom scale, a more upscaled handheld unit or a high-end gym-based unit, more and more people are using them for tracking body composition changes.
But should we use them?
Are they accurate & a valid metric for change or just a fun thing to do?
Let’s dig into that a little!
In essence, body fat testing is not accurate. Is it a valid metric, yes for some higher end athletes, but the majority of end users/the general public won’t see a benefit from their use. They won’t be able to sufficiently replicate the exact same testing conditions, leading to greater inaccuracies and leading the user to believe they gained/lost fat when in fact they haven’t.
Essentially, without cutting you open, all body fat testing is an estimate and based on assumptions regarding the proportions and properties of Fat Mass, Fat Free Mass, water, protein and other minerals.
All composition testing, except skinfold testing, will be subject to impact from your nutrition and hydration and the timing of such.
Depleting some your carbs & being a little more dehydrated will artificially make your body fat look higher. So working out prior to testing isn’t advised. Inversely, eating & drinking prior to testing will make your body fat look lower! Added fluid in your muscles and body, also increasing your level of sodium intake will have an impact!
These impacts exist on all levels of generally available machines used for testing regardless of quality; yes it impacts BIA more than BodPoD or DEXA, but it will impact results nonetheless.
So you want to increase your lean body mass, eat 30 mins prior to testing & make it carb focused….
Like everything we practice at PLT Nutrition & Fitness consistency is key. You need to try and replicate the previous test conditions as much as possible
What Testing Methods Exist?
The most accessible systems are skinfold calipers and BIA "Bioelectrical Impedance Analysis" but some people have access to DEXA & BodPod’s. There are many other forms, but these are less accessible, so we won’t cover those below.
These are generally cheap, a few bucks, though some very expensive ones do exist. They can be bought almost anywhere online and use caliper pressure to a series of specific skinfold sites to measure subcutaneous fat and these measurements are added together.
Pros – generally affordable. Quick and easily accessible home option
Cons – open to error from the skinfold tester using inconsistent site selection
These can be purchased relatively cheap and come in many guises, bathroom scales & handheld units, but also more expensive units such as home scales and even gym-based units such as InBody.
Pros – generally affordable. Quick and easily accessible home options available
Cons – generally inaccurate. The more affordable the more likely to tracking error. The BIA process can be ‘tricked’ by the timing of your nutrition and hydration around testing and also sodium intake.
Air Displacement (Bod Pod)
These use low level dual x-ray frequencies to scan your body
Pros – Regarded as more accurate than BIA.
Cons – Can be expensive. Often accessibility is limited to colleges and medical facilities. Open to error from nutrition and hydration.
Dual Energy X-ray (DEXA)
These are similar to hydrostatic weighing but use air displacement, not water, to estimate your body fat percentage.
Pros – Often regarded as the gold standard (subject to opinion)
Cons – Expensive. Accessibility is very limited to the general public. Not feasible for regular testing. Open to error from nutrition and hydration.
Body fat testing certainly has its place but for the majority of people seeking to lose weight and increase their health they have little merit. The main metrics to take note of will always be the scale, the tape measure and the mirror.