One third of adults already have early liver disease – and a simple tape measure might spot it before it turns serious. New research shows that the ratio between your waist and your height is far better at finding people at risk of liver disease than the long-used body-mass index (BMI). It is quick, cheap and surprisingly accurate – and could become a powerful tool in fighting one of the world’s most rapidly rising health threats.
Researchers say that the reign of the BMI is ending – and for good reason. Now, they are looking for a successor: another easy-to-collect measurement that more accurately identifies people with levels of fat that could put their health at risk.
Recent research points to a promising candidate. The ratio of waist circumference to height (WHtR) shows how much fat is stored deep inside the belly around vital organs. This “hidden” fat is the kind most strongly linked to diabetes, heart disease and other cardiometabolic problems.
It sidesteps many of the pitfalls of the BMI, says Andrew Agbaje, a physician and Professor of Clinical Epidemiology at the University of Eastern Finland in Kuopio.
But the ultimate validation for WHtR is not just whether it is a good surrogate for fat – it is whether WHtR predicts the risk of disease.
Agbaje examined whether WHtR could flag people at elevated risk of metabolic dysfunction–associated steatotic liver disease, which is estimated to affect more than one in three adults worldwide. The findings, published in the Journal of the Endocrine Society, suggest that WHtR is much more sensitive to the risk of liver steatosis than the BMI – flagging people for intervention that would have been missed using the BMI.
Why the BMI gets it wrong
For decades, the BMI has dominated public health messaging on weight and how it affects cardiometabolic health. But fatal flaws with BMI, whose creator explicitly warned that it should never be used to assess a person’s individual health, mean that it is falling out of favour with epidemiologists and other researchers.
First and foremost, Andrew Agbaje says, the BMI is not an effective proxy for what it is supposedly measuring. It cannot distinguish “good weight” such as lean muscle mass from unhealthy levels of fat.
This means that the BMI classifies some very fit people as overweight or even obese when muscle comprises the bulk of their weight, Andrew Agbaje explains. At the same time, some sedentary people may have worrisome levels of fat despite falling into the normal weight category according to the BMI because of low muscle mass.
A simpler, smarter measure: WHtR
If the BMI is dismissed, healthcare providers still need a tool to identify who needs screening for conditions linked to excess body fat, including heart and liver disease. “Not every clinic has a dual energy X-ray absorptiometry (DEXA) scanner, which can measure body fat directly,” Andrew Agbaje says. “But every clinic has a tape measure.”
Waist circumference measurements can enable clinicians to home in on the troublesome kind of fat. Even the bulkiest bodybuilders do not have much muscle at the waist, so additional volume at that point in the torso is attributable to fat surrounding the organs – the most dangerous kind of body fat from a metabolic perspective.
Then, waist circumference is divided by height to account for the fact that taller people have proportionally larger waist circumferences.
In previous studies with children and young adults in the United Kingdom, Andrew Agbaje identified several cutoff points – benchmark WHtR ratios associated with higher body fat percentages as measured by DEXA scanners. But it was unclear whether these cutoff points developed for white children would also apply to adults with different ethnic backgrounds.
Putting WHtR to the test in the liver
Andrew Agbaje aimed to determine whether WHtR could spot people at risk of metabolic dysfunction–associated steatotic liver disease – a slow build-up of fat inside the liver. It often causes no symptoms at first but can quietly damage the liver for years before people even realise it.
If left unchecked, this build-up of fat can crowd out healthy liver cells and impair liver function, ultimately leading to fibrosis – scar tissue that stiffens the liver – and cirrhosis, in which so much of the liver turns into scar tissue that it stops working properly.
To put the WHtR through its paces, Andrew Agbaje analysed data from an ethnically diverse cohort of about 6,500 people in the United States. As part of the National Health and Nutrition Examination Survey between 2021 and 2023, scientists had assessed the liver conditions of thousands of people – ranging in age from preteens to older adults – using ultrasound scans that can detect even early subclinical fat build-up, grading it on a scale from 0 to 3.
But the Survey had also collected weight and body measurements from all its participants. Could either the BMI or WHtR predict each person’s liver steatosis “score” using the scale and tape measure alone?
WHtR much more sensitive to disease
Andrew Agbaje found that WHtR much more effectively predicted liver steatosis than BMI.
BMI did not flag many people as being at risk who had liver steatosis detected through ultrasound. “People can stand on the scale and their weight appears to be normal,” Andrew Agbaje says. “But their liver is already being damaged.”
When he used the WHtR instead, more people with signs of liver disease were correctly flagged for intervention. “WHtR was between three and six times more sensitive to the risk of liver steatosis,” he explains. In practice, this means that people with hidden liver damage were six times more likely to be flagged for follow-up if doctors used WHtR instead of BMI. “If we have 18 people with liver steatosis, only 3 would have been discovered using BMI alone,” he says. “The WHtR would capture all 18.”
Encouragingly, the WHtR worked equally well for people with different racial and ethnic backgrounds. “This overcomes a limitation of BMI, which has real variability across races,” he says.
Where to draw the line – and why it matters
Andrew Agbaje cautions that the reliability of these metrics comes down to the cutoff points – the WHtR numbers that tell doctors when someone’s fat levels have crossed from healthy to risky to dangerous.
Some organisations, including the National Institute for Health and Care Excellence in the United Kingdom and the Department of Defense in the United States, have put forward round numbers such as 0.5 and 0.6 as cutoff points since they would be easier for clinicians and patients to remember. “But science deals with objectivity and not ease of memorisation,” Andrew Agbaje says.
Arbitrary cutoff points can translate to missed opportunities for intervention. Instead, Andrew Agbaje says that scientists must determine the true threshold of risk based on data. In fact, the ultrasound data from this study suggest that liver damage was already detectable among young people with a WHtR ratio of 0.53, well below the 0.6 figure proposed as a threshold of risk by some other researchers.
“That helps us to screen people – to use any opportunity we have to get the disease at an early stage and start interventions that will improve people’s health,” Andrew Agbaje says.
