There was an article in the Sydney Morning Herald this week about people being 'skinny fat'; where people of an apparent healthy weight are simply just skinny, not healthy. Also, just because someone in the overweight category is such, does not mean that they are necessarily unhealthy.
There is a variety of ways of undertaking body composition tests. One of the tools we have in our clinic is our DEXA machine, which is the gold standard for this. It is not uncommon for someone who is traditionally placed in the 'overweight' category, according to BMI to show low body fat levels, paired with high muscle mass levels, just as often someone of apparently normal weight has high fat mass.
What does the research say? Use of DEXA for body composition analysis is the current gold standard, however some factors can affect reliability/validity of results. In particular, what is known as 'biological noise'. A recent paper by Nana et. al (2013) indicates the importance of keeping everything as much 'the same' as possible. Minimal clothing, fasted and well rested if possible provides the most accurate results in the research setting. Food, fluid, exercise and clothing may all affect results.
In practice, we adhere to this as well as we can. Clients strip down to underwear and make use of a hospital gown for each analysis. Where possible, we ask clients to be fasted and rested, however this is not always possible. Instead, we aim to make this as much 'the same' as possible, for example if you are only able to come in on a Monday afternoon for your initial scan, then we ask for you to do the same for any follow ups, and keep your activity level and food intake as similar as possible as well.
But why is it important do do this? Why not just jump on the scales? Does it really matter? My favourite thing about the scan is it lets us see really clearly exactly where a person is at in relation to fat mass and muscle mass. Particularly, if the number on the scales hasn't change much, it helps us to see what has changed, which in this case would usually be an improvement in muscle mass, and reduction in fat mass. Carrying excess fat mass can adversely affect general health, and in some conditions, make symptoms worse (excess fat mass is pro-inflammatory). Further more, it can be very motivating to make the changes you need to make to improve your health, and in some cases, is a necessity for the sport to keep fat mass in check.
We would love to hear about any of your experiences with body composition tests, or if you are interested in getting a scan!
Chloe McLeod is a dietitian at BJC Health.
This blog focuses on diet & nutrition generally and diet & nutrition in relation to the treatment of arthritis and arthritis-related diseases. Contact us if you’d like our help in managing diet-related health issues.