Myth: Everyone with Anorexia has a Low BMI

“She’s a healthy BMI. She’s fine. Teenage girls go through phases. She just needs to eat more.”

This was the response from my GP when I took my daughter to see her about her issues around food. My daughter was 16 and had embarked on a ‘healthy’ diet which had resulted in dramatic weight loss. She’d also lost her periods. And she had confided in me that she was having intrusive thoughts about eating. “And I don’t like it,” she admitted.

Of course, I was aware of anorexia nervosa. We’ve all seen the terrifying photographs of people who look severely malnourished. I had a friend at school who developed the condition in her teens. She became worryingly thin, sallow-cheeked and pale.

My daughter didn’t look like that. She’d even been complimented by a friend of mine on her weight loss. A human’s ability to make his or herself smaller is something to be celebrated, it seems. But the shrinking of my daughter did not make me feel like throwing a party. She had lost a lot of weight very quickly, and her thoughts around food had changed. Plus she hadn’t had a period for three months. That had never happened to me.

Something wasn’t right.

My daughter was weighed and measured. Then the doctor sat her down.

“It’s quite serious,” she said, in a stern tone. “You are in danger of doing permanent damage to your bones and your reproductive system. You need to start eating more.”

And with that we were ushered out of the room. Our ten minutes were up.

No psychological help was offered, no referral to an eating disorders specialist. No help at all, in fact. My daughter was simply told that she should eat more — when the reason we were there in the first place was that she was finding this extremely difficult.

It’s a common story. It happens to many people when they, or their parents, seek help with eating problems. Unless you are underweight according to the BMI chart, the situation, in some doctors’ eyes, doesn’t warrant immediate intervention.

So what is BMI, and is it really a reliable measure of how healthy a person is?

BMI stands for Body Mass Index. According to the World Heath Organisation, BMI is a measure for indicating nutritional status in adults. A person’s BMI can be calculated by a simple sum based on weight and height. Wherever this result sits on the BMI rainbow chart determines which of five categories their body fits into, with ‘normal weight’ being the preferred category, the sweet spot for a healthy human.

It sounds a bit simplistic, doesn’t it? Aren’t populations in some parts of the world a different average size and shape to other populations? Surely this simple calculation isn’t going to work for every body?

So, how did Western medicine come to use BMI to determine how healthy a human is? To understand this, we need to journey back to mid-1800s Belgium, where we find a polymath called Adolphe Quetelet.

Quetelet was an extraordinary man by any measure. A mathematician, astronomer and statistician, he was also fluent in six languages. Quetelet developed an interest in human size and shape and wanted to establish a simple way to classify a person’s weight relative to an ideal for their height. Quetelet wasn’t necessarily motivated by a desire to improve public health; rather he was seeking to find a formula for the ‘average’ man, the homme moyen.

Although his index is still widely used, you’ve probably never heard of Adolphe Quetelet. This is because, in 1972, the Quetelet Index was rebranded as the Body Mass Index by American physiologist Dr Ancel Keys, an intriguing character who has frequently popped up during my reading into eating disorders. Keys is both a hero and a villain of the eating disorders world, having given us the only scientific study into starvation in humans, with important findings for those with an interest in anorexia, and (wrongly) persuaded multiple generations of the inherent dangers of dietary saturated fat.

To give Ancel Keys his due, he did carry out extensive studies to determine the reliability of the Quetelet Index, carefully measuring hundreds of men and checking Quetelet’s findings against his own. Oh yes, incredibly, Keys only looked at men — no children and no women were included — yet BMI was quickly adopted as a measure for all humans.

In recent times, questions have arisen about BMI’s use as a reliable indicator of what an individual’s healthy weight should be. Keys himself acknowledged its flaws, saying that it was “‘if not fully satisfactory, at least as good as any other relative weight index”. And Keys said that BMI was a useful measure for populations. Whether it should ever have been applied to individuals is debatable.

It’s easy to see BMI’s appeal. The BMI chart is simple to use, and it can provide an easy answer to complex questions about a person’s health. Not only that but it comes in pretty colours and looks attractive on the surgery wall. But BMI is not helpful for many people, including people who arrive at the doctor’s surgery with worries about their mental health — like my daughter.

You cannot tell if someone has an eating disorder by the way they look. They may be losing weight but not yet have reached a low BMI. Their weight may be ‘normal’, according to the BMI chart, but their body’s natural set point weight may be higher. So what’s normal according to the BMI chart may be abnormal for them. Also, anorexia nervosa is, first and foremost, a brain-based disorder and should be treated as such.

The truth is that there will always be people who don’t fit into the BMI’s neat ‘normal’ category but are perfectly healthy. People with different ethnic backgrounds differ widely for a start. Not only that, but male and female bodies are not the same, and the human body changes during the ageing process. Humans are not widgets, manufactured on a production line. We are biological beings, and our bodies come in a wonderful array of shapes and sizes, as different from each other as pebbles on a beach.

As for using BMI as a diagnostic tool for anorexia nervosa? Well, I can think of no other mental illness for which you are asked to provide physical proof of your condition before treatment is offered. It would be absurd to insist that someone with any other brain-based disorder must look as if they had that condition before a diagnosis could be made. So why do doctors expect this of someone with an eating disorder?

Doctors, please listen to what people are saying, not what their bodies are telling you. If a person is telling you that something is not right in their mind, it isn’t. They wouldn’t have made an appointment to see you if there wasn’t an issue.

The dangers of sending someone away from the doctor’s office with nothing but an instruction to eat more, as my daughter was that day, can be catastrophic. I’ve heard countless accounts of people having this experience and then suffering a rapid and dangerous decline. It shouldn’t be this way. We know about the importance of early intervention in the outcome of eating disorders. Ignoring someone’s cries for help can leave them stuck in a spiral of unhealthy behaviour for years, causing endless misery, damage to their health and worse.

It’s simply not good enough.

If you have found your worries dismissed by a doctor, please seek a second opinion, and a third if necessary, and a fourth. Keep going until you find a doctor who is willing to listen and understand and offer help. You know when something isn’t right, and sadly you may have to fight to be taken seriously. You may even need to educate your doctor. The charity Beat has a useful leaflet you can print out and give to your doctor which covers the topic of size and more. Print this out and take it with you. Do not give up.

Miraculously, after my daughter was sent away from the doctor’s office that day with an instruction to eat more, she somehow found the strength to do just that. She put on weight and her disordered thoughts diminished. It wasn’t the end of her eating disorder, but she never again lost weight to that degree. Today she is doing well. She is happy.

Her identical twin was not so lucky. Six years on, she is still deep in the eating disorder. The negative thinking is entrenched, and she struggles to eat enough every single day. I often wonder if earlier intervention could have stopped the illness in its tracks, and if we might have avoided years of misery. But we are where we are. Still fighting.