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September 12 2022

Your scale is a big fat liar?

Your scale is a big fat liar?


Your scale is a big fat liar?

To think your scales might have been lying to you about your body fat losses all this time!!! Insert SHOCK HORROR face here______:

In that case what is the best method for tracking your weight loss?

Just to clarify when most people ask to lose weight they actually want to lose body fat NOT weight. So that’s what I’m assuming here.

So which method is best then?

(Read only this for the short answer)

1) Bathroom scales – (Poor Reliability). Use these if you want to measure and keep track of your gravitational pull on this earth. Doesn’t measure body compositional changes i.e. doesn’t tell you squat about the percentage of fat lost vs. muscle gained or visa versa.

2) Skinfolds – (Good Reliability). If you’re on a budget, want site-specific tracking and decent overall estimations then skinfolds are your guy. Downside is it requires a skilled assessor, the right formula and a good pair of calipers to get decent results.

3) Bioelectrical Impedance (BIA): (Quite reliable) if you’re monitoring “weight loss” yourself or poor on time use BIA deceive/scales for quick overall body fat estimations. Bear in mind BIA can have quite poor accuracy (depending) and can also be effected by your levels of hydration.

4) Ultrasound – (Very Good Reliability). Very good for specific tracking of loss in specific body regions. Can be similar to DEXA. Requires expensive device and skilled assessor

5) Use DEXA. (Excellent reliability) for most accurate overall BF % estimations. Very good for site-specific measurements. Can be somewhat expensive

(Read this for the longer more detailed answer)

In order to determine the accuracy of the average bathroom scale I set upon the quest of determining the accuracy of the various methods commonly used today to estimate body fat and “weight” loss.

As mentioned in a previous post, most folk today either use a BMI calculator or even worse just a good old fashioned bathroom scale to track their “weight” gain/”weight” loss. There are several issues with this method see below:


A) Scales don’t distinguish between muscle and fat. Neither can they distinguish between the mush of poop in side of you, your hydration levels or anything else inside of you for that matter. Technically scales don’t even tell you your weight anyway, they tell you your MASS. (Side note: Weight is not measured in kilograms, but in Newton’s. A common misuse of the word)

But anyway moving along…your body “weight” will fluctuate regularly based on changes in muscle, fat, water, glycogen, poop, and a whole bunch of other stuff or your “weight” might stay the same as one decreases and another increases.

CON of Scales:

Long story very short. Don’t look at the scales if your goal is to lose body fat or gain muscle mass. If you want to know your gravitational pull on this earth for sure go ahead and “weigh” your self. But only if it’s actually the number on the scale your interested in tracking.

B) DEXA: Sends a low level X-ray dose through to a reading bed, the denser parts of your body i.e. bone, fat etc. slow down the rate at which the X-ray signal is received, therefore it creates an image of your body composition based on denser parts of the body restricting the signal. Currently this is classified as the “ Gold standard “ next to Hydrostatic weighting which is a method whereby you are fully submerged into a tank of water and have to completely exhale in order for a specially designed scale to estimate your BF.
I suppose the quick 3 min scan in DEXA vs. been partially drowned in a tank of water is slightly easier to administer and deal with when it comes to measuring body composition.


DEXA – can be expensive. Costs range from $50-200+- per scan. So if you are after daily or regular scans, you best make sure you have a qualified practitioner with a DEXA scanner in your close circle of friends.

C) Bioelectrical Impedance analysis (BIA): aka the bathroom scales that also tell you your % of body fat. These are the scales that send an electrical current up one of your legs, through the giggly bits of your body, all the way down to the opposite side. Based on the level of impedance the current is subjected to by the restrictions of fatty masses in your body, it will then spit out a prediction of your overall body fat %. If correctly hydrated there is no statistical difference between leg – leg BIA and hydrostatic weighting . (4).


As you can see from my results (below) different brands of BIM give very different results. TANITA tends to be the best brand out there with the highest rate of accuracy that I’ve come across.

• Cheap EBay version= 17.7% (+7.2% From DEXA)
• Tanita Brand =12.8% (+2.3% From DEXA)

Using a high quality Bioelectrical impedance machine seems to be a reasonable method for daily clinical use, but attention should be paid to the interpretation of % of fat values in both underweight and overweight individuals as these groups tend to have a higher error rate (2). It is also important to note, how much water you’ve had can affect the result. For best results ”weigh” yourself first thing in the morning on an empty stomach after you’ve had a visit from the tinkle fairy.

D) Ultrasound – Ultrasound waves pass through your tissue. Based on the varying structure of the tissue the wave passes back at different rates based on the boundaries it hits. For example, there are strong ultrasound reflections at fat-muscle and muscle-bone junctions. This is how it can estimate the level of fat at a specific point in the body. It is important to note, ultrasound measurements are not affected by hydration, exercise level or caffeine intake and is comparable to DEXA (2). Most importantly much of the research suggests that it is reliable, reproducible and accurate. Ultrasound can measure muscle thickness, as well as differentiate subcutaneous adipose tissue from visceral adipose tissue, limitations of other field techniques.

CON of Ultrasound:

Requires some skill by the assessor. Fascia (a type of connective tissue) could be mistaken for the boundary layer between subcutaneous fat and muscle.

E) Skinfolds: Basically this is getting someone to pinch some skin at specific sites, squeezing them between a pair of calipers and then estimating their total fat based on the sum of the total measurements. Specific formulas are used to predict overall body fat composition. Also just to mention the quality of the calipers matters, the type used can change the estimated value. Harpenden calipers or a good pair of metal calipers and tend to be the most accurate. If correctly administered there is no statistical difference between skinfolds and hydrostatic weighing (4, 3). Good calipers can range from $200-$400.

CON of Skinfolds:

Accuracy changes based on the type of calipers used as well as the skill of the assessor. Skinfolds require someone else to administer the test for you. Several formulas can be used; the formula should be selected based on:

• Age
• Gender
• Ethnic type
• Body type

Ignoring these factors will effect the accuracy of the estimation. Finally skinfolds measure fold thickness rather than tissue thickness and this method is not recommended for assessing obese or elderly individuals(5).

So to answer the question: Which is the best method?

Firstly ask yourself:

1) What do you really want to measure? Fat off your belly? Fat off your bum? or total fat lost off your body ?

Depending on your answer, your price range and your fondness for drowning – the method of measurement will vary

2) The method you use should be done by someone who has good equipment and knows what they’re doing. That’s only if you want accurate measurements of course.

Just remember! What isn’t measured isn’t managed. Or better yet to quote Pete Drucker “What gets measured, gets managed.”

So in a nutshell if you want to manage your weight loss –MANAGE IT properly and whatever method you choose, don’t use a scale!

How to track fat loss in Melbourne:

• DEXA- www.bodyscan.com.au or any other DEXA facility near you
• Ultrasound: [email protected]
• Skinfolds: A qualified assessor – ISAK or similar recommned
• BIA– www.tanitaaustralia.com (Most gyms have these)


1) J Athl Train. Ultrasound Techniques Applied to Body Fat Measurement in Male and Female Athletes. 2009 Mar-Apr; 44(2): 142–147.

2) K Okasora et al Comparison of bioelectrical impedance analysis and dual energy X-ray absorptiometry for assessment of body composition in children
20 JUN 2002

3) European Journal of Clinical Nutrition. Prediction of DXA-determined whole body fat from skinfolds: importance of including skinfolds from the thigh and calf in young, healthy men and women (2005) 59, 695–702

4) Cable A, et al. J Sports Med Phys Fitness 41: 411-414, 2001.

5) Dale R. Wagner. Ultrasound as a Tool to Assess Body Fat 5 June 201

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