In 1972, an American physiology professor Ancel Keys published a landmark paper. It assessed different methods for diagnosing overweight and obesity.

The thinking at that time was that a person’s height and weight could be used to determine how much fat they were carrying. There were various formulas, many of them clunky.

Insurance companies wanted to know what worked best and cheapest.

Ancel Keys launched the BMI’s popularity.

Keys concluded that body mass index (BMI) was a “slightly better”, quicker, simpler and less expensive way to measure obesity.

(To calculate BMI, your weight is divided by your height squared.)

But the thinking behind the formula – that a person’s overall size indicated how fat they were – was fundamentally flawed.

It didn’t account for the fact that muscle is heavier than fat.

Nor did it account for bone density and overall body composition. And weirdly, the distribution and quantity of body fat wasn’t directly assessed.

Nevertheless, the medical world adopted Keys’ findings.

BMI has been the standard tool used by doctors to diagnose obesity ever since.

The superstar factor?

Professor Keys was a superstar scientist.

He developed the K-rations used by the US military in the Second World War. The rations were actually named in his honour.

His experiments in starvation determined the safest way to feed refugees at the end of the war.

In 1962, he was on the cover of Time, celebrated as the man most likely to answer a confounding question. Why had heart disease skyrocketed since the war?

To what extent Keys’ reputation played a part in the BMI’s widespread adoption, who can say?

BMI continues to be the most common measure of obesity across the globe.

The WHO defines a person with a BMI of more than 25 to be overweight. And more than 30 as obese.

But researchers have been trying to kill off BMI for years without success.

Will a new paper prove persuasive?

Last week, the European Association for the Study of Obesity presented “a new framework for the diagnosis, staging and management of obesity in adults”.

The key factor was obesity to be framed as an “adiposity-based chronic disease”.

That is, an assessment of body fat distribution should replace BMI as the core diagnostic variable.

“In many settings, the diagnosis of obesity is still based solely on BMI cut-off values and does not reflect the role of adipose tissue distribution and function in the severity of the disease,” the authors concluded.

What does that mean for patients? Using BMI as the sole diagnostic tool for obesity meant an unknown number of people with the disease were going undiagnosed.

This week, newsGP, published by the Royal Australian College of General Practitioners, ran an endorsement of the findings. 

An imperfect tool

Dr Natasha Yates, a Queensland GP and Medical Education Assistant Professor at Bond University, told newsGP that “many doctors have long been calling for BMI to be abandoned”.

She said: “‘It’s a very imperfect tool, and the problem is that a lot of research has been done using BMI, so when we’re trying to practise according to guidelines, we’re backed into a corner.

‘But we’ve known for a long time that waist measurement is more accurate at predicting cardiovascular risk, and so a lot of GPs are already using that.”

The new study, she said, “will help make sure we’re not missing those patients who are in the BMI range between 25 and 30 who we’ve really wanted to treat but we’ve struggled to have good options for them”.

Using this metric, newsGP advised, Australia is ranked 10th out of 21 OECD countries for the proportion of people aged 15 and over living with overweight or obesity.

This research suggests we have a bigger problem lurking.

Read the full newsGP piece here.