Health, UK (Commonwealth Union) – A recent study has identified a cost-effective alternative to body mass index (BMI) for assessing obesity in children and adolescents: waist circumference-to-height ratio. This new measure more accurately detects excess fat mass and differentiates between fat and muscle mass in this demographic compared to BMI.
Conducted collaboratively by the University of Bristol, University of Exeter, and the University of Eastern Finland, the findings were published in Pediatric Research.
Researchers of the study point out that childhood and adolescent obesity have reached epidemic levels, affecting nearly 1 in 4 young individuals in recent years. Unfortunately, obesity in this population has been linked to various health issues such as cardiovascular, metabolic, neurological, musculoskeletal diseases, and premature death in adulthood. The precise identification of overweight and obesity in children is crucial for timely interventions.
The researchers further indicated that traditionally, weight-to-height ratio charts and BMI for age and sex have been used for diagnosing childhood obesity. However, these methods are flawed in childhood and adolescence as they fail to distinguish between fat and muscle mass. For example, two children with similar BMIs may have different fat-to-muscle mass ratios, making it challenging to diagnose obesity accurately.
Costly tools like the dual-energy X-ray absorptiometry (DEXA) scan offer precise assessments of body fat and muscle content, yet their accessibility in primary health care settings is limited. Responding to this gap, the American Academy of Pediatrics (AAP) issued a clinical guideline urging research into affordable and accurate alternatives for measuring obesity in children.
Recent studies in adults indicate that the waist circumference-to-height ratio may outperform BMI in predicting premature death, suggesting it could complement BMI measurements in diagnosing obesity more effectively. However, there’s a lack of prior assessment regarding the agreement between waist circumference-to-height ratio measurements and DEXA-measured fat and muscle mass throughout childhood to young adulthood. Additionally, the optimal threshold for detecting excess fat in children using waist circumference-to-height ratio remains unclear, prompting this investigation.
This study represents the largest and longest follow-up investigation of DEXA-measured fat and muscle mass globally, utilizing data from the University of Bristol’s Children of the 90s (Avon Longitudinal Study of Parents and Children). The cohort comprised 7,237 children (51% female) aged 9 years, tracked until age 24. Measurements of BMI and waist circumference-to-height ratio were collected at ages 9, 11, 15, 17, and 24 years. Perfect agreement between measurement devices is achieved when they exhibit identical results, typically scoring 100%. For instance, two DEXA scans from different manufacturers would demonstrate nearly perfect agreement in measuring fat mass, scoring between 99 and 100%, according to the researchers of the study.
The waist circumference-to-height ratio demonstrated a substantial agreement, ranging from 81% to 89%, with DEXA-measured total body fat mass and trunk fat mass. However, its agreement with muscle mass was notably lower, ranging from 24% to 39%. Conversely, BMI exhibited a moderate agreement with total fat mass and trunk fat mass, ranging from 65% to 72%, and with muscle mass, ranging from 52% to 58%.
The researchers further noted that given BMI’s moderate agreement with DEXA-measured muscle mass, distinguishing between excess fat and muscle mass becomes challenging. The optimal waist circumference-to-height ratio cut points for predicting the 95th percentile of total fat mass was found to be 0.53 for males and 0.54 for females. These cut points successfully identified 8 out of 10 males and 7 out of 10 females with excess DEXA-measured fat while also accurately identifying 93 out of 100 males as well as 95 out of 100 females without excess fat.
“This study provides novel information that would be useful in updating future childhood obesity guidelines and policy statements. 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. Waist circumference-to-height ratio might be preferable to BMI assessment in children and adolescent clinics as an inexpensive tool for detecting excess fat. Parents should not be discouraged by the BMI or weight of their children but can inexpensively confirm whether the weight is due to increase in excess fat by examining their kid’s waist circumference-to-height ratio.” explained Andrew Agbaje, who is an award-winning physician as well as a pediatric clinical epidemiologist at the University of Eastern Finland.
