Previously in this blog I have drawn attention to the fact that the body mass index (obtained by dividing one’s weight in kg by the square of one’s height in metres) is practically useless as an indicator of health. It seems that far more useful measurements are the waist circumference or what is known as the ‘waist-to-hip ratio’ (waist circumference divided by circumference taken around the hips at their widest point). The bigger these measurements are, the more excess fat there tends to be around the middle of the body. This is important because it’s this type of fatty deposition, known as ‘abdominal obesity’, that is a better predictor of risk of conditions such as heart disease and diabetes than the BMI.
Further support for the value of assessing abdominal obesity has come from a study published this month in the American Journal of Epidemiology. In this research, individuals had what is known as their ‘sagittal abdominal diameter’ measured. Basically, this is the thickness of the body measured at a point midway between the top of the pelvis and bottom of the ribs. Over time, it was found that both men and women with the highest sagittal abdominal diameters, compared to those with the lowest, were more than 40 per cent more likely to develop heart disease. The study also found that individuals who developed higher sagittal abdominal obesity younger in life were more likely to lead to problems with heart disease than those developing overblown bellies later in life. No surprises there!
The take home message is that this study adds further weight to the notion that when it comes to excess weight, the type to avoid is the stuff that gets dumped around the midriff.
The lead author of this study has made a case for the sagittal abdominal diameter to be used in preference to waist circumference, on the basis that it is more ‘standardised’ and probably less prone to error. Yet, as this time we really don’t know if this author’s contentions are correct.
But even if they are, I believe the waist circumference and waist-to-hip ratio should remain as the favoured ways of assessing abdominal obesity. Why? Quite simply because these measurements can be self-administered. This means that anyone who cares to assess themselves can do so, and in the comfort of their own home.
On the other hand, measuring the sagittal abdominal diameter requires a special pair of callipers, and generally needs to be administered by a health professional. As if they didn’t have enough to do.
1. Iribarren C, et al. Value of the sagittal abdominal diameter in coronary heart disease risk assessment: cohort study in a large, multiethnic population. American Journal of Epidemiology. 2006;164(12):1150-1159