Percent body fat adds value to BMI when screening for abnormal blood glucose
medwireNews: Adding body fat percentage (%BF) to BMI improves the classification of individuals at risk for abnormal blood glucose, US researchers report.
Ara Jo and Arch Mainous III, both from the University of Florida in Gainesville, found that individuals with normal weight (BMI 18.5–24.9 kg/m2) who have a high %BF (≥25% in men and ≥35% in women) had a significantly increased risk for abnormal blood glucose (glycated hemoglobin ≥5.7%) compared with those with normal weight and low %BF.
By contrast, overweight (BMI 25.0-29. 9 kg/m2) individuals with low %BF, which was measured by whole-body dual-energy X-ray absorptiometry, were not at increased risk for abnormal glucose.
The researchers say that this is important because the United States Preventive Services Task Force recommends blood glucose screening for adults aged 40–70 years who are overweight or obese according to their BMI.
In addition, the Equal Employment Opportunity Commission recently proposed penalties of up to 30% of health insurance costs for employees that fail to achieve a normal BMI through wellness programmes.
Consequently, BMI can have “substantial implications” when defining someone as low or high risk for abnormal blood glucose, the authors explain.
This cross-sectional study of data from the National Health and Nutrition Examination Survey, 1999–2006, included 6335 individuals aged 40 years and older who had never been diagnosed with type 2 diabetes by a doctor. These participants represented 65,705,694 adults in the US population.
Of the 2587 normal-weight individuals studied, 36.3% had low %BF and 63.7% had high %BF. The corresponding proportions were 9.0% and 91.0% among the 3748 overweight participants.
Jo and Mainous report in BMJ Open that the prevalence of abnormal blood glucose was 8.6% in normal-weight individuals with low %BF, 13.5% in normal-weight individuals with high %BF, 10.5% in overweight individuals with low %BF, and 20.0% in overweight individuals with high %BF.
Compared with normal-weight individuals with low %BF, those with normal weight and high %BF had a significant 1.66-fold increased risk for abnormal blood glucose levels, while the risk was 2.64-fold higher among overweight individuals with high %BF.
By contrast, overweight participants with low %BF were not at significantly greater risk for abnormal blood glucose than normal-weight participants with low %BF.
Similar results were observed when the data were adjusted for age, sex, race/ethnicity, diabetes in first-degree relatives, vigorous intensity activities, and muscle strengthening activities.
The investigators also note that the area under the receiver operating characteristic curve was significantly greater when BMI and %BF were combined (0.5663) than for either BMI (0.5571) or %BF (0.5342) alone.
Jo and Mainous conclude: “Integrating BMI with %BF can improve classification to direct screening and prevention efforts to a group currently considered healthy and avoid penalties and stigmatisation of other groups that are classified as high risk of [abnormal blood glucose].”
By Laura Cowen
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