- Pioneering new research by the University of Sheffield and the University of Nottingham has found that waist-to-height ratio (WHtR) is a more accurate and reliable indicator of age-related obesity risk than body mass index (BMI)
- BMI is a well-known and well understood measure. However, it could be misleading older people and those with less muscle mass into thinking they are not at risk of obesity
- Waist-to-height ratio is also a lot easier for people to understand and remember than more complex BMI categories, particularly in children. A good indicator of a healthy weight is if your waist measures less than half your height
- As the UK population ages and obesity-related diseases increase, researchers say using WHtR as a screening tool could help identify older adults at high risk earlier and improve preventive care
Waist-to-height ratio is a more accurate and reliable indicator of age-related obesity risk than body mass index (BMI), researchers have found.
As the UK’s population continues to age, obesity and obesity related diseases are an increasing burden on the NHS. However, the use of more accurate screening tools such as waist-to-height ratio could help ensure older adults at risk are identified earlier and offered preventive care.
Waist-to-height ratio (WHtR) gives a better representation of visceral fat which is stored around the abdomen and has a greater effect on internal organs which is why it is more important for our health.
The research from the Universities of Sheffield and Nottingham analysed trends in obesity in England between 2005 and 2021 using data from the Health Survey for England. Researchers examined BMI, the most commonly used measure of obesity, alongside other waist-related measures including waist-to-height ratio.
Co-authors Dr Laura Gray from the University of Sheffield and Dr Magdalena Opazo-Breton from the University of Nottingham, explored whether obesity trends were driven mainly by ageing, environmental factors, or generational differences.
Dr Laura Gray, from the University of Sheffield's School of Medicine and Population Health, said: “BMI is a really well-known and well understood measure. However, it could be misleading people, particularly older people and those with less muscle mass, into thinking they are not at risk of obesity.
“Waist-to-height ratio is also a lot easier for people to understand and remember than more complex BMI categories, particularly in children. People can easily check their own risk with a measuring tape. If your waist is less than half your height, that’s a good indicator you’re at a healthy weight.”
She added: “Our findings show that increases in obesity have been largely driven by environmental changes over time, not just individual behaviours, which means we need broader systemic action with policymakers addressing the food environment. The likelihood of obesity also increases with age, meaning that an ageing population could lead to further increases in the prevalence.
“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.”
The findings also show that waist-to-height ratio provides a clearer and more consistent indicator of increasing health risk with age, compared to other measures such as BMI. Unlike BMI, which tends to rise through middle age and then decline in older age, primarily due to muscle loss, waist-to-height ratio continues to increase steadily. Better reflecting how obesity-related diseases such as heart disease, stroke and dementia increase in older adults.
Waist-to-height ratio gives a better representation of visceral fat which is stored around the abdomen and has a greater effect on internal organs which is why it is more important for our health.
The study presents findings that may temper the widespread belief that carrying extra weight in later life can be protective, emphasising instead the importance of maintaining a healthy waist size throughout ageing.
These findings give further support to NICE (National Institute for Health and Care Excellence) who recommends using waist-to-height ratio alongside BMI.
Strengthening the simple public health message of ‘Keep your waist circumference less than half your height’.
The paper: Long-term trends in central obesity in England: An Age-Period-Cohort Approach is published in the International Journal of Obesity. Read the paper in full here
