Findings from the study, conducted by Dr. Margaret Ashwell and Sigrid Gibison, are being presented at the 19th European Congress on Obesity in Lyon, France.
The researchers examined 31 studies involving around 300,000 participants that used specificity and sensitivity analysis for evaluating the discriminatory power of anthropometric indices in individuals with type 2 diabetes, metabolic syndrome, high blood pressure, abnormal body fat levels, and general cardiovascular outcomes (CVD).
They found that compared with BMI, WHtR had considerably greater discriminatory power. WC and WHtR also improved discrimination of adverse outcomes by 3% and 4-5%, respectively, compared with BMI.
Furthermore, WHtR was found to be considerably better for diabetes, CVD, hypertension and all outcomes in men and women compared with WC, and also better than BMI and WC at detecting cardiometabolic risk factors in both sexes. As a result WHtR should be considered as a screening tool.
The average proposed values, i.e. the first risk level for people of different ethnic backgrounds, calculated from the study size for both men and women was 0.5, which was determined in a separate analysis of suggested WHtR cut-off values from the people's specificity and sensitivity analysis.
If you keep your waist to less than half your height measurement, you will probably live longer
In other words, in order to avoid increasing risk of these adverse risk factors "Keep your waist circumference to less than half of your height." According to Ashwell, if a second level of increased risk is needed, keep your waist to below 60% of height (0.6).
WC and BMI both require differing values to be considered for different ethnicities, thus making things considerably more difficult than they need to be. The UK's National Institute for Health and Clinical Excellence are currently considering new guidelines on WC. However, Ashwell states that this would be a waste of resources, as using WHtR instead would be a one-size fits-all approach. This approach is gaining support in a variety of countries, including the UK, USA, Australia, Japan, India, Iran, and Brazil.
Dr Ben Rickayzan and Professor Les Mayhew, from Cass Business School, City University, London, UK, estimate that a 30-year-old non-smoking man could increase his life expectancy by up to 14% if his WHtR is 0.7 and by up to one third if his WHtR is 0.8.
"Keeping your waist circumference to less than half your heigh can help increase life expectancy for every person in the world."