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Study Highlights Effectiveness of Waist-to-Height Ratio Over BMI for Assessing Childhood Obesity
A recent study has revealed that the Body Mass Index (BMI) is nearly three times more likely to label children as overweight compared to the waist circumference-to-height ratio. This significant research was conducted collaboratively by the University of Eastern Finland and the Universities of Bristol and Exeter in the UK, and its findings were published in the journal Obesity and Endocrinology.
BMI, along with weight-to-height ratios, has been widely used to gauge obesity levels among children. However, a key limitation of BMI is its inability to differentiate between lean muscle mass and body fat, leading to potential misclassification of children’s weight status.
In the context of adult obesity, leading health organizations, including the Lancet Commission on Obesity and the European Association for the Study of Obesity (EASO), have advised against relying solely on BMI for diagnosis. They recommend that BMI assessments be supplemented with alternative measures, such as waist-to-height ratio. Likewise, the UK’s National Institute for Health Care and Excellence has endorsed the waist-to-height ratio as a valuable metric for evaluating health risks linked to central obesity in children.
The current study stands out as the largest pediatric follow-up analysis globally, focusing on the comparative effectiveness of BMI and waist-to-height ratio. It involved 7,600 participants from the University of Bristol’s “Children of the 90s” cohort, tracking them from ages 9 to 24. Among the 1,431 children identified as overweight according to their BMI at age 9, only 25% presented with a high ratio of waist-to-height fat, while 64% were classified as having normal fat based on waist circumference data. Conversely, of the 517 children with a high waist-to-height ratio, a significant 70% were classified as overweight by BMI standards, underscoring the potential for BMI to overstate actual obesity levels.
While Dual-Energy X-ray Absorptiometry (DEXA) is regarded as the gold standard for accurate measurement of body fat, it remains an expensive option not readily accessible in all primary health care settings. Prior research indicated that waist-to-height ratio measurements could correlate with DEXA results with an accuracy of up to 85%. The specific cutpoints for categorizing body fat used in this study were based on earlier findings within the same cohort.
Additionally, the waist-to-height ratio cutpoints were externally validated using data from 3,329 US adults for their predictive capability regarding type 2 diabetes. The findings indicated that a high waist-to-height ratio was associated with increased chances of developing prediabetes, whereas an excess fat classification predicted a higher likelihood of type 2 diabetes.
“Waist-to-height ratio is a cost-effective, accessible, and precise tool for identifying children and adolescents with high and excess fat,” stated Andrew Agbaje, a physician and associate professor of Clinical Epidemiology and Child Health at the University of Eastern Finland. His previous research has demonstrated the capability of waist-to-height ratios in predicting overall and central body fat.
Agbaje asserts, “Overweight and obesity diagnoses in children and adolescents should not rely solely on BMI. Instead, waist-to-height ratio should be used for confirmation, especially when DEXA scans are unavailable.”
The study and its accompanying research efforts were made possible through various grants from multiple foundations, including the Jenny and Antti Wihuri Foundation, the Finnish Cultural Foundation, and the Novo Nordisk Foundation, among others.
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