• Waist-to-hip ratio is a better predictor of early death than BMI, according to research being presented at the European Association for the Study of Diabetes (EASD), Stockholm, Sweden.
  • BMI cannot reliably predict the risk of disease or mortality in the same way waist-to-hip ratio does, as it cannot take into consideration where fat is stored in the body.
  • Having higher levels of fat in the abdomen is already associated with an increased risk of heart disease and type 2 diabetes.

Waist-to-hip (WHR) ratio should be used to predict early death over Body Mass Index (BMI), according to research by Irish and Canadian being presented at the European Association for the Study of Diabetes.

BMI has long been used to assess a person’s weight, with a BMI of 18.5-24.9 considered a healthy weight range. However, scientists believe BMI should not be used to predict an individual’s risk of disease or mortality because it does not consider where fat is stored within the body.

“BMI doesn’t take into account fat distribution,” said Irfan Khan, a medical student at the College of Medicine and Health, University College Cork, Cork, Ireland.

“It doesn’t consider where fat is stored – whether it’s accumulated around the hips or the waist. As a result, BMI doesn’t reliably predict the risk of disease or mortality.

“We wanted to find out whether waist-to-hip ratio (WHR) or fat mass index (FMI) would more reliably predict mortality across different fat distributions.”

The researchers first established that higher levels of fat cause an increase in mortality by analysing data from UK Biobank participants with genes associated with the risk of weight gain or obesity.

Following this, measures including BMI, WHR, and FMI were applied to the Biobank data of over 25,000 Caucasian men and women whose health had been tracked until their death.

A relationship between WHR and death from any cause was shown to increase linearly, demonstrating that when an individual’s WHR was lowest, so was their risk of early death. The risk of early death then increased alongside increases in WHR.

On the other hand, those with extremely high or low BMI or FMI had an increased risk of mortality compared to individuals with a moderate BMI or FMI.

The relationship between WHR and all-cause mortality was also consistent across different fat distributions, which was not apparent in BMI and FMI.

“BMI’s major limitation is that it doesn’t take into account differences in fat distribution,” Mr Khan continued. “This could mean that someone who has accumulated fat around their waist will have the same BMI as someone of the same age and height who stores their fat around the hips, despite the health risks of abdominal fat.

“WHR, however, better reflects levels of abdominal fat, including visceral fat, which wraps around the organs deep inside the body and raises the risk of a range of conditions, including type 2 diabetes and heart disease.

“With WHR the message is simply: the lower the WHR, the lower your mortality risk.”

Mr Khan says the results need to be replicated in individuals of diverse genetic ancestry. However, these current results suggest that having a lower WHR is better, regardless of the population studied. Alternatively, optimal BMI variates depending on the population, meaning a one-size-fits-all approach does not work.

Mr Khan concluded: “Clinical recommendations and interventions should prioritise setting healthy WHR targets rather than general BMI targets.

“A more accurate measure of a healthy body shape may make a significant difference to the ill health and deaths caused by type 2 diabetes, heart disease, some cancers and numerous other conditions.”

This article is from an early release due to be presented at the European Association for the Study of Diabetes (EASD) Annual Meeting in Stockholm, Sweden (19-23 Sept).

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