Say Bye Bye to BMI: Why The Body Mass Index has been removed from the 2024 Australian Curriculum

Content warning: discussions of weight and briefly eating disorders.

As of February 2024, after multiple advocacy campaigns, over 340 mentions of BMI, dieting, calorie counting and ‘good’ or ‘bad’ foods have been removed from the Australian Curriculum.

This is after multiple research papers have found that these concepts are more harmful to young people than beneficial. So why is this? What is wrong with the BMI anyway? And how will this benefit Australian young people?

*The Revised Australian Health and Wellbeing Curriculum. Source: ACARA*

Origins of the BMI

BMI is a simple formula based on a person’s weight and height which gives a two-digit number. When you are under a certain two-digit number you are considered ‘underweight’ and when you are over certain numbers you are considered ‘overweight’ or ‘obese’. Seems simple enough right?

Well, I hate to break it to the BMI purists, but a health professional didn’t create it nor does it adequately reflect the entire population. It was actually made by a Belgian mathematician, Adolphe Quetelet in the 1830s not to diagnose obesity, but to find the so-called ‘average man’.

Adolphe Quetelet, the creator of the BMI mathematical model.

Source: Getty Images.

Not only did Quetelet’s study fail to find the average man, but his research practices were also very average as he only measured healthy men, all of whom were from Western Europe.

The 1970s was when the BMI really emerged with American physiologist Ancel Keys promoting Quetelet's index as the best available for obesity screening. While they increased the measurement sample slightly, keys only measured 8000 ‘healthy’ men from 12 different (primarily Western) sample groups.

So, if you are female or from those countries outside of the sample groups, the BMI was not made nor should be used for you. However, in reality the BMI should be used for no one as Quetelet explicitly said over 200 years ago that his index should not be used to diagnose individual weight-based problems. Here’s why…

Why the BMI statistically sucks

Dwayne 'The Rock' Johnson, I'm not one to make assumptions but I am 99% sure he is not 'Obese'.

Source: Shutterstock images.

It assumes that all people have low muscle mass and high relative fat content: Whilst this might work for people who are not active, even slight exercise makes it less accurate. The BMI considers elite athletes; some of the fittest people around, overweight or oven obese. For example, if I put wrestler and Hollywood superstar Dwayne ‘The Rock’ Johnson’s approximate height and weight into a BMI calculator it would output an obese result when I am 99% sure he is in fact not obese.
It also assumes that people of all ages are physiologically the same: This is not true as our body parts change significantly with age. A prime example of this is bone density with bones becoming the most dense at ages 20-30, meaning they are significantly heavier during those years than in other stages of our lives.
It suggests defined categories of weight with the difference between being underweight and overweight for everyone being down to decimal places in an arbitrary formula which is just not true.
It is bad data practice: There is no physiological reason to square the height, which Quetelet did originally to manipulate his formula to his overall data.
It lies under the illusion of scientific authority: Those with a higher BMI, despite being perfectly healthy, can be brushed off at the doctors' office or charged extra health insurance premiums unnecessarily, making some people with a higher BMI avoid seeking medical attention entirely.

BMI and wider dieting culture in schools

In Australia, 22% of the adolescent population, 33% of girls and 13% of boys aged 11-19 met the criteria for an eating disorder. When compared to obesity teachers, parents, school staff and medical professionals have a lesser understanding of eating disorders which is partially the reason why the BMI has been taught in schools for so long.

Tasks that used to be encouraged by the curriculum such as calculating other people’s BMI in a maths or biology class, classifying foods as strictly ‘good’ or ‘bad’ in nutrition, or counting calories in a food diary for health and well-being merely support the myth of the ‘perfect body’ that is already so pervasive in social media and advertising. School is supposed to be a safe space for students, and for those who are already insecure about their bodies, fuelling that insecurity with a false metric is not only unproductive but can be extremely damaging to students’ mental health and pre-existing eating habits.

The much-welcomed removal of BMI is only the beginning of a broader understanding that our bodies are not binary, there is no magical number that tells us exactly to the percentile when we start becoming ‘overweight’, no one-size-fits-all all approach to the way we fuel ourselves or one way to foster a strong relationship with our bodies.

Whilst the current changes to the curriculum are a good starting point, the BMI is still over-utilised in other contexts such as in medicine, as a general indicator of overall health. So next time you encounter the BMI in your lifetime, know that in some contexts, when combined with other tests, it can be a small indicator of some specific things, like heart health and that unless explicitly advised by a qualified health professional, BMI is not something to compare yourself to or plan your health goals around.

It’s just a silly little number created by some Belgian guy which is now super outdated.

Support

If you are in a crisis situation or need immediate assistance:

000 Emergency
000
triplezero.gov.au
Available 24/7

If you are concerned about eating disorders or body image issues:

Butterfly National Helpline
1800 33 4673
butterfly.org.au
Available 7.30am-11.30pm, every day

If you need mental health support:

Kids Helpline
1800 55 1800
kidshelpline.com.au
Available 24/7 for 5-25 year olds

Lifeline
13 11 14
lifeline.org.au
Available 24/7

References

Australian Curriculum Assessment and Reporting Authority 2024, Food and wellbeing | V9 Australian Curriculum, Home | V9 Australian Curriculum, viewed 9 April 2024, <https://v9.australiancurriculum.edu.au/teacher-resources/understand-this-curriculum-connection/food-and-wellbeing#accordion-9f3107eb3b-item-6bedc1d84b>.

Bullivant, B., Denham, A.R., Stephens, C., Olson, R.E., Mitchison, D., Gill, T., Maguire, S., Latner, J.D., Hay, P., Rodgers, B. and Stevenson, R.J., 2019. Elucidating knowledge and beliefs about obesity and eating disorders among key stakeholders: paving the way for an integrated approach to health promotion. BMC Public Health, 19, pp.1-10.

Bye bye BMI: Food and wellbeing education in schools overhauled to prevent eating disorders in young people — TheEmbraceCollective 2024, TheEmbraceCollective, viewed 9 April 2024, <https://theembracecollective.org/blog/bye-bye-bmi-food-and-wellbeing-education-in-schools-overhauled-to-prevent-eating-disorders-in-young-people>.

Cook, H 2024, Diets, BMI and ‘bad’ foods axed: Eating disorders prompt curriculum overhaul, The Sydney Morning Herald, viewed 9 April 2024, <https://www.smh.com.au/national/diets-bmi-and-bad-foods-axed-eating-disorders-prompt-curriculum-overhaul-20240131-p5f1bp.html>.

Humphreys, S., 2010. The unethical use of BMI in contemporary general practice. British Journal of General Practice, 60(578), pp.696-697.

Mitchison, D., Mond, J., Bussey, K., Griffiths, S., Trompeter, N., Lonergan, A., Pike, K.M., Murray, S.B. and Hay, P., 2020. DSM-5 full syndrome, other specified, and unspecified eating disorders in Australian adolescents: prevalence and clinical significance. Psychological medicine, 50(6), pp.981-990.

Stabouli, S., Erdine, S., Suurorg, L., Jankauskienė, A. and Lurbe, E., 2021. Obesity and eating disorders in children and adolescents: the bidirectional link. Nutrients, 13(12), p.4321.

Top 10 Reasons Why The BMI Is Bogus 2009, NPR, viewed 9 April 2024, <https://www.npr.org/templates/story/story.php?storyId=106268439>.

Truu, M 2022, The really old, racist, and non-medical origins of the tool we use to measure our health, ABC (Australian Broadcasting Corporation), viewed 9 April 2024, <https://www.abc.net.au/news/2022-01-02/the-problem-with-the-body-mass-index-bmi/100728416>.

Why BMI can be a faulty measure of overall health 2022, PBS NewsHour, viewed 9 April 2024, <https://www.pbs.org/newshour/health/why-bmi-can-be-a-faulty-measure-of-overall-health>.