Did you know that the Body Mass Index calculation is a simple calculation invented back in the 1830s by a European (Belgian) to determine if a person's weight is healthy, overweight or underweight? It is a simple formula which you can calculate easily online with your height and weight, try it here:
At this point though, we need to proceed with caution!
The qualifying guidelines for bariatric surgery in Australia are 'a BMI of 40 and above, or 35 and above with co-morbidities'. It is a quick and easily calculation, but it is flawed! The reality is that your full medical history is considered when the assessment is done for weight loss surgery, then successful surgery is not just measured by your weight in the future. Coming off long term medications and reducing risk of disease are potential outcomes too.
Five reasons why BMI is flawed:
It does not factor muscle mass. If a person is overweight or obese, they will have significantly more muscle mass since every movement is carrying around additional weight. This is the same for athletes with high muscle mass.
It is not accurate for people who retain a lot of fluid. This is a side effect of some medications and for some medical conditions.
It is more accurate for Europeans and not very accurate for other ethnic groups for example, Aboriginal and/or Torres Strait Islander Peoples, Pacific Island Peoples and people of Asian/South Asian descent.
It is not accurate for young people (19 and under).
It is not accurate if you are pregnant.
Even though BMI is used as one of the inputs for determining surgery eligibility, it becomes less relevant as you lose weight.
Is your muscle mass increasing as you lose weight and become more active with exercise?
Was your muscle mass higher to start with, so BMI was not an accurate measure for your healthy weight?
What does a healthy weight mean for you? Is it a measure on the scales, or are there other factors like how clothes fit, how active you are, how you feel and how other health conditions improve?