WAIST CIRCUMFERENCE, AND not body mass index (BMI) is the most accurate way of measuring obesity, a new study has found.
Researchers at the Department of Economics at NUI Maynooth have found that both BMI and Bioelectrical Impedance Analysis (BIA) misclassified large numbers of individuals, but that this is not the case with waist circumference.
The researchers started from the hypothesis that there is no strong basis for choosing any single measure of obesity as a gold standard.
The study looks at how competing measures give conflicting results in the same patients and examines the patterns of responses across the entire sample to estimate the underlying error rates of each test. The statistical analysis provides estimated error rates of 3% for waist circumference, compared to error rates as high as 50% with BMI and BIA.
In Ireland, men are considered obese if their waist is over 37 inches and women over 32 inches.
Discussing the findings, Professor Donal O’ Neill, said: “Reliable measures of body composition are essential in order to develop effective policies to tackle the costs of obesity. The problem with body mass index is not that it misclassifies non-obese people as obese but rather that it fails to truly detect obesity when it is present. The issue with bioelectrical impedance analysis is the very high probability of a false positive.
Our findings have important policy implications, both in terms of how we measure the growth in obesity over time and also in terms of how we evaluate racial gaps in obesity.
“Since our analysis suggests that measures based on waist circumference accurately reflect the true prevalence of obesity and since waist circumference measures of obesity have grown in excess of what would be predicted given the growth in body mass index, it is quite possible that we are underestimating the extent to which obesity has grown over time.”
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