Research presented as this year’s European Congress on Obesity shows that waist-to-height ratio (WHtR) is a better predictor of mortality risk than body mass index (BMI). The research is by Dr Margaret Ashwell, Ashwell Associates and Oxford Brookes University, UK, Professor Ben Rickayzen and Professor Les Mayhew both at Cass Business School, City University London, UK, and colleagues.
In the study, the authors compared the effect of central obesity (WHtR) and total obesity (BMI) on life expectancy expressed as years of life lost (YLL), using data on adults from the Health Survey for England (HSE) and Health and Lifestyle survey (HALS). The number of YLL at three ages (30, 50, 70 years) was found by comparing the life expectancies of obese lives with those lives at optimum levels of BMI and WHtR (waist divided by height). Previous research by Ashwell and colleagues has shown that WHtR could be a better tool for predicting cardiometabolic risk factors than BMI.
In this latest study, the authors found that mortality risk associated with BMI with this British data was similar to that found in US studies. However, significantly, the study found that WHtR was a more accurate indicator of mortality risk than BMI. This was demonstrated by the authors finding a clearer correlation between WHtR and mortality rates than BMI and mortality rates (see link to tables below)
For the first time, data have been produced to quantify YLL at different values of WHtR. This has been done for both sexes separately and for three representative ages. For example, for a man aged 30 years with a BMI in the highest category considered of over 40 (0.8% of men that age), the predicted YLL is 10.5 years. Under the WHtR method, for the most severely obese category considered (ratio 0.8, representing 0.2% of the population), YLL was 16.7 years. When considering 50 year old women with a BMI of over 40 (3.0% of women that age), YLL is 5.1 years. Under the most severely obese category considered for WHtR, (ratio 0.8, representing 0.7% of women that age), the YLL was 8.2 years (see linked table and poster for other examples).
The authors say: “This study supports the simple message ‘Keep your waist circumference to less than half your height’. The use of WHtR in public health screening, with appropriate action, could help add years to life. If health professionals included this simple measurement in their screening procedures then many years of productive life could be saved.”
Link to full abstract
Source: European Congress on Obesity (ECO)