Waist-to-Height Ratio Tops BMI for Predicting Child Obesity

(HealthDay News) — Waist circumference-to-height ratio (WHtR) is an inexpensive alternative to body mass index (BMI) for predicting fat mass (FM) in pediatric patients, according to a study published online March 5 in Pediatric Research.

Andrew O. Agbaje, M.D., Ph.D., from the University of Eastern Finland in Kuopio, examined agreement of surrogate measures of adiposity with dual-energy X-ray absorptiometry-measured body composition. The analysis included 7,237 9-year-old children participating in the Avon Longitudinal Study of Parents and Children, with 15-year follow-up data.

Agbaje found that during follow-up, BMI, total FM, and trunk FM increased, but WHtR was relatively stable. Over time, WHtR provided better absolute agreement with total FM as well as trunk FM (males: intraclass correlation [ICC], 0.84; females: ICC, 0.81) compared with BMI (males: ICC, 0.65; females: ICC, 0.72). For predicting excess total FM (75th to 95thpercentile), the WHtR cut point was 0.50 to 0.53 in males (area under the curve [AUC], 0.86 to 0.94; sensitivity: 0.51 to 0.79; specificity: 0.93 to 0.95). In females, the WHtR cut point for predicting excess total FM was 0.52 to 0.54 (AUC, 0.83 to 0.95; sensitivity: 0.38 to 0.68; specificity: 0.92 to 0.95). For trunk FM, results were similar.

“This study provides novel information that would be useful in updating future childhood obesity guidelines and policy statements,” Agbaje said in a statement. “The average waist circumference-to-height ratio in childhood, adolescence, and young adulthood is 0.45; it does not vary with age and among individuals like BMI.”

What is waist circumference-to-height ratio (WHtr)?

Waist circumference-to-height ratio, often abbreviated as WHtr, requires dividing your waist circumference measurement by your height measurement. This calculation reflects the distribution of fat around the abdomen concerning an individual’s height. The rationale behind this ratio lies in the understanding that excess abdominal fat, particularly visceral fat, poses significant health risks, including cardiovascular diseases, type 2 diabetes, and metabolic syndrome.

Height is key to this ratio as it provides a reference point for interpreting waist circumference. Individuals with similar waist circumferences but differing heights will have distinct WHtr’s, reflecting variations in body composition and fat distribution. Taller individuals typically have larger waist circumferences due to their greater body mass, yet their WHtr may remain within healthy ranges if the fat distribution is proportional. Conversely, shorter individuals may exhibit lower waist circumferences but higher WHtr if they have excess abdominal fat relative to their height.

A high WHtr is consistently linked with an increased risk of cardiovascular diseases, insulin resistance, hypertension, and mortality. Research suggests that WHtr could be a better indicator of health compared to traditional measures such as body mass index (BMI) in predicting these health risks, particularly in populations with varying body compositions. Additionally, WHtr offers advantages over waist circumference alone by accounting for individual differences in height, thus providing a more personalized assessment of health risks.

Why BMI doesn’t always work for Black Americans

Black Americans tend to have different body compositions compared to other racial or ethnic groups. They often have higher bone mineral density and muscle mass relative to their height compared to Caucasians. BMI does not differentiate between fat mass and lean mass, leading to misclassification of individuals with higher muscle mass as overweight or obese when they may have a healthy body fat percentage.

Health care providers should be cautious when using BMI as the sole measure of health status or risk among Black Americans. Other measures like WHtr, waist-to-hip ratio, or more advanced techniques like dual-energy X-ray absorptiometry (DEXA) scanning can give a wider evaluation of body composition and health risks among Black populations.

WHtr represents a diverse and accurate determinant of healthy size due to its ability to assess abdominal fat while accounting for variations in body size. This ratio gives valuable insights into an individual’s health status and risk of chronic diseases, making it an indispensable tool for health assessment and risk mitigation.

Abstract/Full Text

Read More About Pediatrics