Waistline of 102 centimetres in men and 88cm in women indicate obesity. iStock
Waistline of 102 centimetres in men and 88cm in women indicate obesity. iStock

Weighty problem for scientists as effectiveness of BMI is called into question



You may have read the press coverage, seen the social media or noticed the posters. Whatever way, you will know the Ministry of Health is working hard to get the nation back in shape.

Everyone knows the problem – with almost two-thirds of the population overweight or obese, the health of the UAE is going pear-shaped.

Still, maybe you’re one of the lucky, healthy minority.

You may know your Body Mass Index (BMI) – that is, weight in kilograms divided by the square of height in metres – is below the figure of 25 officially regarded as overweight, let alone the 30 figure deemed obese.

If so, it is time to wipe that smug smile off your face.

New research has confirmed concern that the BMI is not a reliable way of telling if you are unhealthily fat.

An international study of more than 41,000 people in Australasia and Europe has shown it is entirely possible to have a healthy BMI and still face a 60 per cent higher risk of early death from cardiovascular disease.

The results, in the current issue of Obesity, show that the global obsession with BMI (even the World Health Organisation uses it) has obscured the greater reliability of a much simpler measure: waist circumference.

The rule could hardly be more basic.

Get a tape measure and put it around the narrowest part of your torso. If you’re a man and the figure is at least 102 centimetres, then you’re obese. For women, the figure is 88cm.

That’s it: no need to fret about measuring your weight, or how to square your height. Apparently what really matters is just the size of the spare tyre around your waist. It is that which holds the key to ill-health from overeating.

This may be good news for some people, as those waist measurement standards are pretty hefty.

Indeed, the researchers found that 6 per cent of people with obese BMIs may not, in fact, be at greater risk – because their waist measurements are just fine.

But there is bad news for the similar proportion of people whose BMIs are fine but whose waist measurements are anything but.

They typically face a 30 per cent increased risk, and double that in the under-65s.

While it may be unreliable on its own, a BMI exceeding 30, combined with an obese waist circumference, was linked with up to a doubling of the risk of death from cardiovascular disease.

If you find all this depressing, spare a thought for obesity researchers. For them, this is just the latest evidence that their field is a scientific basket-case.

As governments look to them for reliable insights into combating the global obesity epidemic, they are having to face the fact that they have even got some of the basics wrong.

The whole debacle is a salutary lesson in the dangers of so-called “physics envy”, believing that what has worked for the most successful of sciences can perform miracles elsewhere.

There is no doubting the success of physics in its own terms. When it comes to predicting the properties of subatomic particles or clashing black holes, it has been brilliantly successful. The recent discoveries of the Higgs boson and gravitational waves bear witness to that.

But that success comes largely from the fact that, despite their apparent complexity, physics problems can often be simplified and summed up using equations. And these lead to grand assertions with a decent chance of proving correct.

It is a strategy that has not worked well in the “softer” sciences, with their far harder challenges – like nutrition.

Take the case of the BMI. This took shape back in the 1830s in the work of a Belgian statistician named Adolphe Quetelet, who was keen to sum up human characteristics in mathematical form.

His studies of the weight and height of humans led him to claim that the former tended to be proportional to the square of the latter.

Why this “law” should hold is not clear but that didn’t prevent his ideas being picked up by the insurance industry looking for a simple test for those who are “disproportionately” hefty, and thus likely to die early.

By the 1970s, Quetelet’s law had been given a new name – the BMI – and had become central to research into obesity. It has stayed there ever since, impressive-looking, unexplained and – it is now clear – unreliable.

The study in Obesity makes a strong case for ditching the BMI from the toolkit of dietary science. But the wonder is it didn't happen decades ago.

Fans of sports such as boxing and rugby have long had access to data that reveals there’s a big problem with BMI. All it takes is a calculator and the height and weight of some heroes of these sports.

Many of these elite athletes turn out to have BMIs consistent with them being overweight slobs.

Charles Martin, the current IBF world heavyweight boxing champion, has a BMI of more than 29, which is borderline obese.

It’s nonsense, of course. The BMI formula simply cannot cope with the fact that muscle is more dense than fat, thus cramming more mass into a given height, and fooling the formula. Yet do not hold your breath waiting for BMI to be disavowed by researchers. They have proved remarkably resistant to ditching dodgy practices.

Despite repeated warnings, they still try to find links between diet and ill-health via studies that ask people to record their eating using diaries.

Unsurprisingly to anyone but, it seems, nutritionists, the results have proved unreliable.

This month, in a scathing analysis of almost 50 years of such studies, Dr Edward Archer, of the University of Alabama, said that people understated what they ate to the point where the data was “incompatible with survival”.

Even so, the findings of these studies are now the basis of US government dietary advice.

Even that most basic law of dieting – that a calorie is a calorie, implying it is quantity not quality that matters – has proved to be nonsense.

Lifted straight from the physicist’s playbook, this bit of thermodynamics holds true for simple systems like engines.

But shovel 2,000 calories of sugar daily into human “engines”, and they will need drastic repairs far sooner than those getting those calories via fish, fruit and vegetables. Human biochemistry is a tad more complex than a steam engine.

It is clear that governments have been fed a diet of pseudoscience by experts for decades. The proof can be seen breathlessly waddling around us every day. We deserve better.

Robert Matthews is visiting professor of science at Aston University, Birmingham. His new book, Chancing It: The Laws of Chance and What They Mean for You, is out now.

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Company Profile

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The alternatives

• Founded in 2014, Telr is a payment aggregator and gateway with an office in Silicon Oasis. It’s e-commerce entry plan costs Dh349 monthly (plus VAT). QR codes direct customers to an online payment page and merchants can generate payments through messaging apps.

• Business Bay’s Pallapay claims 40,000-plus active merchants who can invoice customers and receive payment by card. Fees range from 1.99 per cent plus Dh1 per transaction depending on payment method and location, such as online or via UAE mobile.

• Tap started in May 2013 in Kuwait, allowing Middle East businesses to bill, accept, receive and make payments online “easier, faster and smoother” via goSell and goCollect. It supports more than 10,000 merchants. Monthly fees range from US$65-100, plus card charges of 2.75-3.75 per cent and Dh1.2 per sale.

2checkout’s “all-in-one payment gateway and merchant account” accepts payments in 200-plus markets for 2.4-3.9 per cent, plus a Dh1.2-Dh1.8 currency conversion charge. The US provider processes online shop and mobile transactions and has 17,000-plus active digital commerce users.

• PayPal is probably the best-known online goods payment method - usually used for eBay purchases -  but can be used to receive funds, providing everyone’s signed up. Costs from 2.9 per cent plus Dh1.2 per transaction.

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KEY DATES IN AMAZON'S HISTORY

July 5, 1994: Jeff Bezos founds Cadabra Inc, which would later be renamed to Amazon.com, because his lawyer misheard the name as 'cadaver'. In its earliest days, the bookstore operated out of a rented garage in Bellevue, Washington

July 16, 1995: Amazon formally opens as an online bookseller. Fluid Concepts and Creative Analogies: Computer Models of the Fundamental Mechanisms of Thought becomes the first item sold on Amazon

1997: Amazon goes public at $18 a share, which has grown about 1,000 per cent at present. Its highest closing price was $197.85 on June 27, 2024

1998: Amazon acquires IMDb, its first major acquisition. It also starts selling CDs and DVDs

2000: Amazon Marketplace opens, allowing people to sell items on the website

2002: Amazon forms what would become Amazon Web Services, opening the Amazon.com platform to all developers. The cloud unit would follow in 2006

2003: Amazon turns in an annual profit of $75 million, the first time it ended a year in the black

2005: Amazon Prime is introduced, its first-ever subscription service that offered US customers free two-day shipping for $79 a year

2006: Amazon Unbox is unveiled, the company's video service that would later morph into Amazon Instant Video and, ultimately, Amazon Video

2007: Amazon's first hardware product, the Kindle e-reader, is introduced; the Fire TV and Fire Phone would come in 2014. Grocery service Amazon Fresh is also started

2009: Amazon introduces Amazon Basics, its in-house label for a variety of products

2010: The foundations for Amazon Studios were laid. Its first original streaming content debuted in 2013

2011: The Amazon Appstore for Google's Android is launched. It is still unavailable on Apple's iOS

2014: The Amazon Echo is launched, a speaker that acts as a personal digital assistant powered by Alexa

2017: Amazon acquires Whole Foods for $13.7 billion, its biggest acquisition

2018: Amazon's market cap briefly crosses the $1 trillion mark, making it, at the time, only the third company to achieve that milestone