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From the Journals

BMI Misses the Mark in Kids, Study Finds

BMI overestimated the prevalence of overweight in childhood by nearly threefold, according to a new study comparing it with waist circumference-to-height ratio.

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A new study comparing body mass index and waist-to-height ratio for evaluating adiposity in children found that BMI overestimated the prevalence of overweight by up to threefold compared with waist-to-height ratio.

Conducted by Andrew O. Agbaje, MD, and colleagues, the research analyzed data from 7,600 children enrolled in the Avon Longitudinal Study of Parents and Children in the United Kingdom.

Published in Obesity and Endocrinology, the study reported that body mass index (BMI) overestimated the prevalence of overweight by 2.8-fold in childhood, 2.3-fold in adolescence, and 2.6-fold in young adulthood compared with waist-to-height ratio (WHtR). Among the 1,431 children classified as overweight based on BMI, 25% had WHtR-defined high fat, 11% had excess fat, and 64% were classified as having normal fat.

“Nearly two-thirds of children classified as BMI overweight had WHtR-estimated normal fat,” said Dr. Agbaje of the Institute of Public Health and Clinical Nutrition at the University of Eastern Finland.

WHtR was also found to be more strongly associated with cardiometabolic risk than BMI. In an external validation using U.S. data from 3,329 adults in the National Health and Nutrition Examination Survey, WHtR-defined high fat predicted increased risk for prediabetes, and excess fat was associated with higher odds of type 2 diabetes based on fasting plasma glucose.

To support implementation of WHtR in pediatric practice, the study proposed sex-specific cut points. For males, a WHtR less than 0.40 was considered low fat, 0.40 to 0.49 as normal fat, 0.50 to 0.52 as high fat (adiposopathy grade 1), and 0.53 or higher as excess fat (adiposopathy grade 2). For females, the normal fat threshold extended up to 0.50, high fat ranged from 0.51 to 0.53, and excess fat was defined as 0.54 or higher.

Although BMI and WHtR were strongly correlated across ages, the study found poor absolute agreement between the two measures. BMI also underestimated underweight by 7.5-fold in childhood compared with WHtR.

The authors concluded that WHtR can be adopted universally as a noninvasive and inexpensive tool for diagnosing and monitoring excess adiposity in pediatric populations.

Full disclosures are available in the study.