When was the last time you measured your waist-to-hip ratio? If you're like most of us, probably never. But here's a compelling reason to start.
A new study, published in Nutrition, Obesity and Exercise, suggests that this simple measurement may be linked to cognitive decline. Individuals with smaller waists compared to their hips were found to have a significantly lower risk than those with larger waists.
Concerned about your numbers? Don’t stress just yet – researchers emphasise that your risk isn’t set in stone. By making healthier dietary choices, you can actively reduce your risk of cognitive decline and support long-term brain health.
Out with BMI, in with waist-to-hip ratio
Most scientists measure body size with the body mass index (BMI), which compares weight to height. However, this system has been widely criticised as inaccurate. For instance, muscular people may be classed as overweight even though their heaviness may not put them at risk of developing diseases such as type 2 diabetes or heart disease.
Scientists have therefore increasingly turned to alternative measures of body size, such as body roundness – which measures the waist in relation to height – and waist-to-hip ratio, which the authors of this study said was a more accurate measure of size-related health risk than BMI because it focuses on abdominal fat.
“We found a relationship between a healthier waist-to-hip ratio and better working memory and executive function scores, which has implications for how independent people are later in life,” study author and neuroscientist at the Max Planck Institute, Dr Daria E. A. Jensen, told BBC Science Focus.
The study, published yesterday, investigated the links between diet, body size and brain health over several decades. The waists and hips of 664 British civil servants were measured five times over approximately 21 years in their fifties and sixties.
Assessing diets and measuring brain health
A group of 512 civil servants also answered questionnaires about their diets three times between the ages of 48 and 60 on average. The scientists measured dietary quality by measuring 11 different components, including vegetables, fruits, whole grains, nuts, legumes, fats, sugary drinks, meat, salt and alcohol.
When the participants were approximately 70 years old, the scientists then took brain scans and measured cognitive performance. They found that people with better diets and slimmer waists in middle age had healthier brains later in life.
The scientists used brain imaging techniques – magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) – to examine participants’ brain structure, particularly focusing on a region called the hippocampus.
“The hippocampus is important within dementia research – and a lot of other research – because it’s the key brain area for memory and learning,” said Jensen. She explained that previous studies had already demonstrated the importance of hippocampus volume, but this study focused on how connected the hippocampus was to different areas of the brain.
“What we first found is that better diet was related to higher functional connectivity of the hippocampus with other brain areas,” said Jensen. “Then we looked into waist-to-hip ratio and found really, really strong effects, showing that a slimmer waist related to improvements in white matter connectivity, which means better communication between brain regions.”
People who ate healthier diets and had slimmer waists in midlife were therefore found to be more cognitively healthy later in life, and less at risk of developing diseases such as dementia.
“If you want to do something for your brain health, it is not too late to do something now, but the earlier you start, the better,” said Jensen.
There were some problems with this study. Because the participants were civil servants recruited in the 1980s, only 20 per cent were women, which Jensen said was “very important,” as further studies would be needed to confirm how relevant these results were for women.
But, she said, the study was still “very exciting” and would allow scientists to study the relationship between nutritional health at midlife and brain health in future.
The Alzheimer’s Society estimates that 982,000 people are currently living with dementia in the UK. Jensen said she hoped this study would help “shift the focus of medical doctors more and more towards prevention,” when it came to dementia and cognitive decline.
About our expert:
Dr Daria E. A. Jensen is a postdoctoral fellow at the Clinic of Cognitive Neurology, University Medical Center Leipzig and the Neurology Department of the Max Planck Institute for Human Cognitive and Brain Sciences in Germany. She is also a visiting researcher at the Department of Psychiatry, University of Oxford and corresponding author of this study.
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