• Bonny

What you NEED to know about "weighing" yourself.

Ahh those bathroom scales. We go through periods of loving them or hating them. For many, it’s a frustrating love/hate relationship that needs to be clarified.

Fear not gentle reader as I guide you through a better understanding of tools to measure body composition.


For some it can trigger anxiety, however.. there is more to it than just a number.. (YOU are more than just a number). The human body is comprised of bones, organs, muscle, fat and water. You could be carrying a fair bit of water weight but the scales will only give you a total number. If you were to gain lean muscle (which we want), the scales can go up.. but that doesn’t mean you’re any less healthier because the number has increased.

I’ll give you an example. Recently I woke up after a stressful day- I had unfortunately lost my appetite from being so stressed (as well as performing physical activity to help manage the anxiety). My weight dropped down to 53.9kg from a steady 54.7kg. Likely I was in a calorie deficit combined with loss of lean muscle tissue. If I only focused on numbers, I would be quite pleased. However, I knew for a fact I would have LOST muscle due to feeling reduce muscle tone. How I FELT physically says more to me than any number.

Key message: the number on the scale doesn’t give you a clear picture of how much is fat mass, lean muscle mass or WATER (compositions that actually vary). Don’t feel discouraged with these numbers but to simply use it as a baseline/ starting point.

Physical differences

Examining any changes to the physical shape and tone of your body is an excellent method in assessing your progress. Like I said before, scales aren’t accurate, but the mirror and how you feel, reflects the physical changes on your body. You may notice fat around the stomach to be reduced, or your biceps have increased or your face appears less puffy or bloated.

Key message: Notice any changes to muscle tone, areas that are prone to carrying fat mass, bloatedness and overall physical, metabolic and mental changes :)


Belt getting tighter or looser.. and need to change the buckle hole?

Pants getting uncomfortable or falling off your waist?

Fitting into clothes you haven’t worn in years?

Key message: Changes to your clothes can be a good indicator of body changes. It just depends on which direction you want to be headed..

Waist circumference (WC)

The most dangerous site to be carrying excessive fat is around the abdomen, where body organs are surrounded by fat and can’t function properly (eg. fatty liver disease). As WC comes down, your risk of developing cardiovascular disease and other metabolic conditions are also reduced.

For women: risk of disease is increased >80cm and risk is high >88cm.

For men: risk of disease is increased >94cm and risk is high >102cm.

Key message: a simple method in assessing changes around your stomach area. Measure the narrowest part of your torso- between rib cage and belly button- (get someone to help if needed). Monitor weekly if you have a fair bit of weight to lose.


The Body Mass Index (BMI) takes into consideration your weight in relation with your height.

To work out your Body Mass Index:

BMI= Weight (kg)

Height (m)2

Table 1. BMI chart for adults (1)

Table 2. BMI chart interpretation (2)

As mentioned above, scales may tell you that you’re heavier/ lighter but what exactly changed? The same goes for the BMI chart, yes your height has been established on the chart, but the weight that you’re sitting on, again doesn’t tell you whether its fat, muscle or water. A heavy-built rugby player with lots of muscle can be charted as overweight (25kg/m2)or even obese (>30kg/m2), but they’re not physiology an unhealthy obese person..

The BMI chart also doesn’t factor in age group (elderly, under 18, people with physical disability, body builders or high performance athletes) (2).

Key message: I would use the BMI chart to determine your ideal weight range according to your height, and that’s it. Ask yourself, what weight you feel your best at.

Skinfold testing

If you don’t enjoy being pinched or tickled, this one is not for you. A skin fold caliper is used to pinch the surface of the skin to grab hold of subcutaneous fat, the fat sitting underneath the skin. 3-9 sites on your body (chest, abdominal, thigh/quadricep, tricep, shoulder blade/lower tip, hip front, armpit at fifth rib) are measured 3 times to get an average. With this average, they plug it into an equation/ online calculator to estimate body fat percentage (3).

Be aware this method is subject to human error (if I was to measure, I’d likely to measure inaccurately due to my uncoordinated nature).

Key message: Using a calculated body fat percentage, you can then see if it changes. But due to it being subjective to human error .. it’s more of an estimate.


Bioelectrical impedance method (BIA) sends an electric current through the water content in your body(4,5).This is on the basis that muscle holds more water, whereas fat holds none.. It then gives you a reading of your body fat percentage, lean muscle mass percentage, water weight and bone mass (kg).

Image A. My BIA results from Aug 2017. Unlikely accurate as I'd been eating and drank my cup of tea prior to measuring. 

Thing is, water composition can fluctuate significantly, thereby resulting in inaccurate readings.Physical activity can result in higher lean muscle and lower body fat readings(6)Dehydration has been found to cause a 5kg underestimation of lean muscle(7)Post meal measurements (body fat %) have also been found to be lower compared to pre-meal(8)

Key message: Take this reading with a grain of salt, it is used to estimate fat-free body mass and body fat but it will not be 100% accurate due to water weight fluctuations. DEXA scanA DEXA (Duel energy x ray absorptiometry) scan is the gold-standard of measuring body composition. I repeat, GOLD-standard. This means it is the most ACCURATE (9,10). Two x-rays measure bone mineral density and fat mass and free fat mass are calculated(11). However, DEXA scans do cost money so if you were prepping for a body building/ bikini competition or along those lines, you wouldn’t necessarily need to have a DEXA scan done.

But for those of you who are determined, it could be your driving force.

(approx $160.00)

Key Message: DEXA scans are very accurate in measuring body composition

Conclusion (PLEASE READ): Its easy to get caught up with numbers on the scales especially when you’ve worked hard and you WANT to see results. Don’t get discouraged. Instead, focus on performance markers (number of steps walked per day, ability to climb up stairs without feeling puffed, lifting heavier weights with less effort). Aim for Clinical and performance goals, and the body composition goals will follow.

Until next time,

~ Bonny C References

1. National Health and Medical Research Council. Clinical Practice Guidelines for the Management of Overweight and Obesity in Adults, Adolescents and Children in Australia [Internet]. 2013 [cited 26th Oct 2017]. Available from:

2. Health Direct Australia. Body Mass Index (BMI) and waist circumference [Internet]. 2016 [cited 26th Oct 2017]. Available from:

3. Peterson, Dan. 7-Site Skin Fold Test Calculator for Calculating Body Fat Percentage [Internet]. 2017 [cited 26th Oct 2017]. Available from:

4. Xiao J, Purcell SA, Prado CM, Gonzalez MC. Fat Mass to Fat-free mass Ratio Reference Values from NHANES III using Bioelectrical Impedance Analysis. Clinical Nutrition. 2017 Oct 6.

5. Ohta M, Midorikawa T, Hikihara Y, Masuo Y, Sakamoto S, Torii S, Kawakami Y, Fukunaga T, Kanehisa H. Validity of segmental bioelectrical impedance analysis for estimating fat-free mass in children including overweight individuals. Applied Physiology, Nutrition, and Metabolism. 2016 Oct 14;42(2):157-65.

6. Abu Khaled M, McCutcheon MJ, Reddy S, Pearman PL, Hunter GR, Weinsier RL (May 1988). "Electrical impedance in assessing human body composition: the BIA method". Am. J. Clin. Nutr. 47 (5): 789–92

7. Lukaski HC, Bolonchuk WW, Hall CB, Siders WA (April 1986). "Validation of tetrapolar bioelectrical impedance method to assess human body composition" (PDF). J. Appl. Physiol. 60 (4): 1327–32.

8. Slinde F, Rossander-Hulthén L (October 2001). "Bioelectrical impedance: effect of 3 identical meals on diurnal impedance variation and calculation of body composition". Am. J. Clin. Nutr. 74 (4): 474–8.

9. St-Onge, M-P; Wang, J; Shen, W; Wang, Z; et al. (2004). "Dual-energy X-ray absorptiometry-measured lean soft tissue mass: Differing relation to body cell mass across the adult life span". The Journals of Gerontology Series A: Biological Sciences and Medical Sciences.

10. Wells JC, Fewtrell MS. Measuring body composition. Archives of disease in childhood. 2006 Jul 1;91(7):612-7.

11. Van Der Sluis, I M; De Ridder, MA; Boot, AM; Krenning, EP; De Muinck Keizer-Schrama, SM (2002). "Reference data for bone density and body composition measured with dual energy x ray absorptiometry in white children and young adults". Archives of Disease in Childhood. 87 (4): 341–7; discussion 341–7. PMC 1763043