BMI (body mass index) is an antiquated, inadequate, and potentially racist measure of health. The formula – body mass divided by the square of the body height – was devised in the nineteenth century not by a physician by a mathematician, Lambert Adolphe Jacques Quetelet, as a quick and easy way to measure the degree of obesity in the general population and  assist his government in allocating its resources.

At the population level, the index is somewhat predictive, making it useful to epidemiologists. But it is not predictive of anything much at the individual level, and was never meant to be.

Which is why I was rather surprised last week when I got a text from a friend and fellow parent – who also happens to be a clinical psychologist – asking me if my daughter was okay. She was concerned because apparently our eighth graders had been made to calculate and report on their own BMI in class.

I checked in with my daughter.

‘Walk me through it,’ I said, and she opened the online workbook entitled Nutrition Unit.

A question in the workbook prompts: How Healthy are you?

Next, the children are directed to an NSW government URL, the Make Healthy Normal quiz.

We took the quiz together, punching in her height and weight and sliding a little bar up and down to indicate how much water she drank, how many serves of veggies she ate per week, etc. I hit Enter and was horrified to see a sad frowny-face emoticon appear on the screen, accompanied by the words ‘underweight’ and ‘unhealthy’.

‘Is that why you didn’t go for a run today?’ I asked.

‘Yeah,’ she admitted.

Fabulous, I thought sarcastically, slamming the laptop shut. Just what our teenagers need during a global pandemic: another neurosis.

My daughter, who is perfectly healthy but of slight build like her mother and father and every other member of her family going back generations, has stopped exercising because her health class has freaked her out. At an age when our kids are not only less active than ever, but also at the greatest risk of developing eating disorders, and at a time when their mental health is at an all-time low due to the ongoing pandemic, they are sitting alone in their bedrooms being told they are too fat or too thin via the use of emoticons.

‘At least the pedagogically worthless colour-in sheets they have my second grader doing in lockdown aren’t likely to kill him!’ I raged to whoever was listening.

An overreaction? Hardly. The mortality rate for some eating disorders can run as high as 10 per cent. Comparing that to the 0.004 per cent infection fatality rate for Covid 19 in this age group, kind of puts things into perspective: we need to take adolescent body image seriously.

Of course, the aetiology of eating disorders is complex, and it is unlikely that a single event like having to calculate your BMI in health class could cause anyone to develop one in the absence of any other factors. However, for those kids already at risk, a seemingly small event can act as a catalyst. In my own research on gymnasts, many of the girls can trace their pathological behaviours around food back to a single comment made by a coach or skin fold test taken in early adolescence. And, while the prevalence of eating disorders in these elite athletes is astronomical, the mere mortals among us are not immune. Eating disorders and disordered eating are estimated to affect 16.3 per cent of the Australian population or roughly four million of us. In adolescents, that figure goes up to around 27 per cent with the average age of onset between 12 and 25 years.

If you thought this is only a problem for skinny rich white girls, you’d be wrong. Socioeconomic status has little to do with it, boys are only slightly less effected than girls, and Indigenous populations are at greatest risk.

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Interested to know how the other thirteen-and-fourteen-year-olds in my daughter’s class had responded to the BMI test, I did a quick ring around.

One mother told me she had caught her ‘underweight’ daughter trying to fix the problem by scoffing an entire tub of ice-cream. Another told me that her son – who has just had a massive growth spurt – felt devastated at the false accusation that he was underweight and had become obsessed with consuming protein. In both these cases, the health lesson had resulted in disordered eating, which is the most significant risk factor for the onset of a full-blown eating disorder.

The conversation I had with the father whose daughter is already battling anorexia was equally disturbing. He told me: ‘That frowny-face to her is like a gold star’.

On the flip side of course were the kids who’d been informed, with an even more severe frowny face this time, that they were overweight. I spoke with one sensitive and intelligent young woman of Tongan descent who was recently diagnosed with hypothyroidism, a medical condition affecting metabolism. She told me about the relentless bullying and how humiliating and unhelpful it felt to be labelled and to be asked to report on that label in front of her teacher and peers. From her perspective, it had nothing to do with being protected from hard truths, it was just nobody else’s business; they didn’t have all the facts, and neither were they entitled to them.

Australia: right now, our teens are doing it tough. They are not snowflakes. They are tolerating severe limitations in their own lives to keep the rest of us safe. They are missing friends, school, exercise, socialising and community. They are sad and frightened. They are staring at screens all day long and being bombarded with perfect-looking social media fraudsters. The last thing they need is to be branded as unhealthy through the medium of emoticons.

To undo the damage done to my daughter, I brought up the Centre for Disease Control Growth Charts. We had a long talk about bell curves and the concept of normal distribution. Her weight places her on the 10th percentile, and, put like this, she could clearly see that someone has to be in that bottom 10 per cent; more than 2.5 million Australians in fact (I made her do the maths). I also pulled out her old NSW Health Blue Book – the record of her early development – to show her that, since birth, the 10^th percentile is where she has sat, and probably always would. What I was able to give her, which was missing from the health lesson and certainly not conveyed in an emoticon, was context and conversation.

‘Do you eat three balanced meals a day with snacks of fresh fruit and veggies?’ I asked her.

‘Yes, you make me.’

‘And do you eat cookies and pancakes sometimes too and feel good about it?’

‘Yeah.’

‘And do you move your body?’

‘I walk 40 minutes a day to and from the bus stop. And I play hockey and run.’

‘And do you have the energy for all that?’

‘I don’t know.’

‘Well, is your body managing to grow still and are you getting your period?’

‘Mum! Yes!’

‘Then do you think you’re healthy?’

‘I guess so.’

Later that day, exhausted, I tweeted the NSW Department of Education. Their response was to admit the problem, but pass the buck back to the school:

Thanks for bringing this to our attention. Measuring student’s weight in class is a highly sensitive issue and is not recommended by the department. The BMI is not an index suitable for children. If you haven’t already, please speak with the principal to express your concerns.

Sure thing. I’m pretty busy educating two of your pupils right now but I’ll add ‘write angry Karen letter to Mr. what’s-his-name’ to my list. If an NSW government website is being used in a NSW school, then where does the accountability for that lie if not the NSW Department of Education itself?

Part of the problem is that the subject in question, Personal Development, Health and Physical Education (PDHPE) is a camel of a subject – a horse designed by committee – containing a bloated curriculum. Teachers are expected to teach the rules of cricket alongside a hodgepodge of wellness and life skills that used to be the domain of, well, society itself. The syllabus is overstuffed with lofty and vague promises, such as that children will develop

Strategies to manage change, challenges, power, abuse, violence and learn how to protect themselves and others in a range of situations.

Hard going, when you’ve also got to get this distractable and unruly lot to participate in mixed-sex dance classes while not emotionally terrorising one another or throwing balls at one another’s heads. Harder still, when you’ve got to teach the subject formally known as ‘Sport’ virtually. Blaming teachers, who are struggling to find content so that they can deliver lessons online during the pandemic, is not helpful. The time would have been far better spent for everyone had the kids been told to go outside and jump on the trampoline, the teachers sat back with a nice cup of tea, and the department spent the day stripping the curriculum back to basics.

The real health lesson here is an old one: first, do no harm.