Anyone who knows me will be aware that I have a particular dislike for Body Mass Index (BMI) as a means of assessing risk in those who are overweight or obese. The mere fact that BMI was invented in the 19th century should be enough to make us look for an alternative, but despite its manifest inadequacies, the use of BMI is remarkably persistent. For many years researchers have been looking for simpler and more accurate predictors of complications such as diabetes, heart disease etc in those with weight problems. A better alternative to BMI is the waist measurement, but this requires that everyone can remember what is a “safe” waist measurement and there are differing cut-offs depending on ethnic origin.
Now researchers have come up with a much simpler alternative which is easy to remember and applies whatever your ethnic background: the waist/height ratio. Put simply, if you divide your waist measurement by your height (in inches or cms) the answer should be less than 0.5. So for a 5ft 5” (65 inches) woman with a waist measurement of 42”, her waist/height ratio is 0.6 which puts her at increased risk of heart disease, diabetes, certain cancers etc. A 6ft male, on the other hand, would need a waist measurement of 35” for a ratio of 0.49 – just under the cut-off point.
In the study, researchers used a technique called meta-analysis to determine which combination of the various anthropometric measures (height, weight, waist etc) works best for predicting weight-related health problems such as type 2 diabetes, hypertension and heart disease. A total of 31 studies were included in the analysis involving more than 300,000 adults in various ethnic groups. Although waist measurement alone was a good predictor of outcomes (better than BMI), the waist/height ratio was significantly better than waist measurement alone or BMI.
So whatever your nationality, the message is to keep your waist/height ratio below 0.5.
Dr David Ashton MD PhD
20th May 2013