Measuring someone’s waist-to-height ratio is a “much better indicator” of the health risks associated with carrying excess fat than body mass index (BMI), particularly in older people, according to a recent study (Gray, 2025).
BMI does not highlight where fat is stored, and as people lose muscle as they age body fat percentage may go up despite the number on the scales coming down, experts said.
Using a tape measure to assess waist-to-height ratio may help pinpoint people who have more fat stored around their vital organs, which can put health at risk, they suggest.
How the Measures Differ
BMI is calculated by dividing a person’s weight in kilograms by height in metres squared.
Whereas WHtR is calculated by measuring your waist circumference and dividing it by your height.
A normal waist-to-height ratio (WHR) is generally considered to be below 0.5, meaning your waist measurement should be less than half your height.
Whilst ratios of 0.5 to 0.59 indicate increased risk and 0.6 or higher suggest a high risk for health problems like type 2 diabetes, hypertension, and heart disease.
According to researchers, if the circumference of the waist is less than half a person’s height, it is “a good indicator” they are at a healthy weight.
Whilst BMI may decline in old age due to muscle loss, waist-to-height ratio may continue to increase steadily and better reflect the risk of conditions such as heart disease and stroke.
Dr Laura Gray, of the University of Sheffield’s School of Medicine and Population Health (lead author of the study) said:
“BMI doesn’t account for any muscle in your body. Weight could be fat weight or muscle weight, and it doesn’t distinguish between the two. That’s problematic.”
“This study is the other side of that coin. Older people tend to lose muscle when they age, and that means that their body fat percentage is actually higher, but their weight has still dropped, so BMI starts coming down, but actually they’re getting less healthy.
“Waist-to-height ratio, because it measures round your waist, it’s giving us a more accurate measurement of visceral fat.”
Study Findings
The study, published in the International Journal of Obesity and led by researchers at the universities of Sheffield and Nottingham, analysed obesity trends between 2005 and 2021 using data from the Health Survey for England.
They found waist-to-height ratio provides a clearer picture of health risks with age compared to BMI.
Gray said: “If we under-diagnose obesity in older adults because we’re relying solely on BMI, then this could mean we fail to identify large proportions of people who are at high risk and can benefit from healthcare interventions. People are more likely to have obesity the older they get, and that’s been the case for some time.
Practical Implications
Gray suggests the method may even save money.
“Tape measure is actually cheaper than a set of weighing scales,” she said. “It’s probably easier because it’s just a ratio, rather than squaring something like we do with BMI.”
The study also found the environment has a “significant influence” on obesity.
“It’s not that people have changed, it’s that society’s changing.”
Figures show that in 2023-2024, 64.5% of adults in England were estimated to be overweight or obese, with 26.5% classed as living with obesity.
Gray concluded: “BMI was originally developed to measure obesity in a whole population. So, on an average, when you’ve got those people with low muscle and high muscle on average, it works quite well over a whole population. But it’s for individuals where it falls down a bit.”
Calculate your waist-to-height ratio (NHS website)
