What new research about the limits of the body mass index might tell us about obesity

Good morning.

In 2022, a study by The Lancet found that obesity among adults had more than doubled since 1990, and quadrupled among children and adolescents. As these figures continue to rise, experts are increasingly questioning how to better identify, manage and prevent obesity.

This week, an international commission of 58 experts called for a “radical overhaul” of the way obesity is diagnosed, raising concerns about the limitations of body mass index (BMI) as a diagnostic tool. The commission is advocating for “a more accurate” and “nuanced” definition of obesity. Their report, developed over the course of a year, suggests rethinking obesity as a “spectrum” rather than a singular disease.

Is there a better way? For today’s newsletter, I spoke with Prof Sadaf Farooqi of the University of Cambridge, a member of the report’s steering committee, about the implications of this new approach to understanding obesity. But first, this morning’s headlines.

Five big stories

In depth: ‘People have recognised the problem with BMI for a long time’

The origins of BMI can be traced back to 1833. The standardised – and highly contentious – weight metric was devised by a Belgian statistician to describe the “average man”. The current iteration of the BMI calculation was developed in the 1970s by an American physiologist and subsequently adopted as a primary indicator of health.

There is a clear link between body fat and adverse health effects such as type 2 diabetesand heart disease. However, the absence of an easy, precise method to measure a person’s fat levels has led to an over-reliance on BMI, which is calculated by dividing an adult’s weight in kilograms by the square of their height in metres. The core issue with BMI is that it focuses solely on body weight and does not differentiate between muscle and fat, or account for more dangerous fats found in specific areas of the body.

The report urges doctors to assess a patient’s overall health rather than relying solely on BMI, which has proven to be an unreliable indicator of individual health. This dependence can lead to under-diagnosis of those seen to be lean and over-diagnosis of those who are presumed to be obese because of their BMI.

“People have recognised this problem with BMI for a long time. A person, for example a rugby player, with high muscle mass will register as obese, but to suggest that this person is at high risk of heart disease would be inaccurate,” says Farooqi. BMI remains useful when researchers examine entire populations, Farooqi notes, “but it’s not so great when giving individual health advice”.

What are the main changes in the report?

Recognising the various limitations of BMI, the Lancet report aims to collate evidence and highlight alternatives to better identify individuals whose health is adversely affected by their level of body fat. As a result, the report recommends two new categories of obesity: clinical and pre-clinical. The former applies to those whose chronic illnesses and diseases are directly caused by their weight, while the latter refers to individuals who are healthy but face an elevated risk of developing issues in the future. The intention is to reflect that people with obesity have a diverse range of life experiences and health outcomes.

The report also advocates for the use of additional indicators, such as measuring a person’s waist or waist-to-hip ratio, alongside directly asking questions about how their weight might be affecting aspects of their health, including their joints, fertility, blood pressure and mobility.

Why has change been so slow?

Though there have been significant social and cultural movements that have championed body acceptance and pushed for equal treatment of fat people, the medical conversation around obesity has remained stagnant for many years. Experts have long criticised the strict adherence to BMI, as it fails to provide a meaningful assessment of who might require medical intervention.

One clear reason for BMI’s persistence is its simplicity and convenience. Another is the inherent challenge of establishing a definition that finds broad international consensus. “I think the key was getting everybody together behind a single solution, and that’s really what this commission did. It was a very exhaustive process; you can see the long list of people from around the world – everybody got to have their say,” Farooqi says.

Why is it important to reframe obesity in this way?

For many decades, there have been very few treatments for obesity. That is no longer the case, Farooqi explains: “We now do have them, and they are effective,” referring to semaglutides (better known under brand names such as Ozempic or Wegovy). “There’s an even clearer rationale for this report because it lays out who might benefit from this treatment, which can have dramatic effects on people’s health, including reducing their risk of heart attacks.”

Defining clinical obesity in this way paves the way for more personalised, targeted care. The experts behind the report hope it will enable individuals with clinical obesity, who have often been dismissed by healthcare professionals, to access proper medical evaluations and treatments. “What often happens is people are just repeatedly told to go on a diet and exercise, but what this report recognises is that clinical obesity is a disease that should be assessed with the same rigour as conditions like asthma or high blood pressure.”

Conversely, it also ensures that those at risk but without current health issues are not over diagnosed, and avoids misdiagnosing individuals with higher weight due to muscle mass.

“I think this is a gamechanger,” Farooqi says. “It’s a really powerful piece of work that redefines one of the major health problems of our time. It allows us to see the clinical problems, recognise its prevalence in society, and most importantly, to help destigmatise obesity.”

What else we’ve been reading

• After the death of David Lynch, Peter Bradshaw pays tribute to “a film-maker who found portals to alternative existences and truffled in them like they were erogenous zones”. Lynch’s vision, he writes, was of a world that is “normal on top, weird underneath, but these layers can’t exist without each other”. Archie

• Charlie Brinkhurst-Cuff’s piece on the killing of Fiona Holm and how the police failed two Black women who sought their protection from the same abuser is crucial reading. It examines why certain victims who go missing are treated with less urgency by the police, media and state than others. Jason Okundaye, assistant editor, newsletters

• Yannick and Ben Jakober began amassing 165 paintings of children at the Museum Sa Bassa Blanca after the death of their daughter aged 19. In this poignant piece, Anna Parker meets the couple in Mallorca on how art has been a medium for tragic family histories. Jason

• Americans seem to have decided to hate Robbie Williams without even knowing who the Take That singer is. Harsh, but fair? Either way, it’s bad news for his monkey biopic, Better Man, which is bombing after being picked up by Paramount for US distribution for $25m. Toby Moses, head of newsletters

• Ciaran Thapar speaks to jailed British rapper Marnz Malone on the mental health crisis affecting prisoners and how music has served as a more effective rehabilitation than detention. Jason

Sport

Premier League | Amad Diallo scored three times in 12 minutes to earn Manchester United a 3-1 victory over Southampton after they had trailed the league’s bottom side for most of the game. Goals from Kaoru Mitoma and Georginio Rutter fired Brighton to a 2-0 victory at relegation-threatened Ipswich.

Cricket | Australia beat England by a comfortable 86-run margin in the third one-day international in Hobart, taking a commanding 6-0 points lead in the Women’s Ashes. Ash Gardner rescued the hosts from 59-4 with a run-a-ball century before England lost their last six wickets for 22 runs.

Tennis | Men’s no 5 seed Daniil Medvedev was stunned by US qualifier Learner Tien in a five-set thriller in the second round of the Australian Open yesterday. Today, top seed Aryna Sabalenka went safely through to the fourth round in the women’s draw and Britain’s Jacob Fearnley fell in straight sets to Alexander Zverev. Follow the latest here.

The front pages

The Guardian leads with “No Israel vote on deal ‘until Hamas agrees to all terms’” while the Times has “Looser loan rules could get economy on the move”. Top story in the Daily Mail is “Labour blasted over ‘toothless’ grooming probes”, while “Why aren’t you wanting to find out the real truth?” is a Daily Express story on a grooming gang victim.

The i splashes on “UK army now ‘too small’ to play a major peacekeeping role in Ukraine”. The Daily Mirror goes with “Elianne’s life mattered … her legacy will live on” after a stabbing murder conviction – “Justice is done but our hearts are broken” is the Metro’s version. “BP’s under-fire boss cuts 4,700 jobs in fight to revive shares” – pick up the Financial Times to read that one.

Something for the weekend

Our critics’ roundup of the best things to watch, read, play and listen to right now

Film
A Complete Unknown | ★★★★★
Timothée Chalamet’s hilarious and seductive portrayal of Bob Dylan makes him the smirking, scowling and unwilling leader of his generation, whose refusal to submit to the crucifixion of folk-acoustic purity is his own crucifixion. Chalamet is a hypnotic Dylan, performing the tracks himself and fabricating to a really impressive degree that stoner-hungover birdsong. He is also good at Dylan’s insolent comedy in art as in life: puckish, witty, insufferable and yet wounded. You might not buy Chalamet’s Dylan at first; I didn’t. But there is amazing bravado in this performance. Peter Bradshaw

TV
The Crow Girl | ★★★★☆
The most striking thing about The Crow Girl is the sight of young male bodies lying dead all over the place. It’s quite shocking. Those poor boys, you think. Isn’t it terrible? How could anyone … ? It has the twin effects of drawing you deeper into the plot and showing you how inured we have become to the sight of young dead female bodies used as scenery and plot points. It’s good to be reminded now and then, I think, of what we deem normal and where we draw our cultural lines and have our consciousnesses and consciences shaken awake. Lucy Mangan

Book
Good Girl by Aria Aber
Nila is the wild, rebellious daughter of Afghan doctors who fled their home before she was born and settled in a brutalist social housing block in Berlin. After 9/11, the family learned to lie (“To resent ourselves with precision”), to hide parts of themselves that seemed too much like “those people”; Muslims in a city where Nazis were alive and well. Then her mother died, and Nila began looking for a way out. Venturing out of her neighbourhood, she saw “people drinking mulled wine at Christmas markets, and between them, everywhere, there was a Mohammed or an Ali or an Aisha trying to get by”. And she hated them, “hated everyone who had the same fate as I did … I was ravaged by the hunger to ruin my life.” Dina Nayeri

Music
Mogwai: The Bad Fire | ★★★★☆
Mogwai’s 11th album commences with an icy electronic arpeggio enveloped in reverb. Beneath, other, deeper, darker synthesiser tones build and glide. The effect is both faintly ominous and cinematic, perhaps because the sound bears a resemblance to the electronic scores that director John Carpenter devised for his movies in the late 70s and early 80s. It’s a suitably grand and portentous opening for The Bad Fire, an album that coincides with Mogwai’s 30th anniversary. Alexis Petridis

Today in Focus

Cartoon of the day | Ben Jennings

The Upside

A bit of good news to remind you that the world’s not all bad

The service station stop-off is a staple of any journey across the UK, and every motorist has their favourite (shout-out to Beaconsfield on the M40). Now, archaeologists working in Gloucester have recently discovered that this is anything but a modern fixture of life – uncovering a 2,000-year-old Roman precursor to the prepacked sandwich and overpriced coffee.

The Roman mutatio – a horse-changing station – would have provided travellers with a much-needed rest as they made their way on the Ermin Street road, linking Gloucestershire andHampshire. Hundreds of Roman coins, brooches, animal bones and the remains of ovens have been discovered at the eight hectare settlement, discovered as part of a much bigger site where up to 70 archaeologists have worked across the past two years.

Alex Thomson, the project manager for Oxford Cotswold Archaeology, said: “Being able to look at a Roman roadside settlement in such extensive detail is a rare opportunity. It’s clear that the structures we’ve recorded helped serve the passing trade on a busy Roman highway.

“Cirencester was the second-largest Roman settlement outside of London in Britain. And Gloucester was a very important centre for the military. They may have been servicing passing legions as they marched along the road.”

Bored at work?

And finally, the Guardian’s puzzles are here to keep you entertained throughout the day. Until Monday.

• Quick crossword

• Cryptic crossword

• Wordiply