The use of body mass index (BMI) class to assess disease severity can lead to underestimated disease burden in a substantial proportion of children with class 1 obesity and overestimated health risk in children with class 3 obesity, according to study results published in The Lancet Child & Adolescent Health. Combination of BMI with a staging system accounting for metabolic, mechanical, mental health, and social milieu issues might be more accurate.

Although BMI is a very common measure to define obesity and its severity, its usefulness in assessing health burden is less known. In this study, the researchers examined associations between BMI class and the Edmonton Obesity Staging System for Pediatrics (EOSS-P), a more specific and clinical staging system that includes metabolic, mechanical, and mental health measures, as well as social background.

Patients were classified into BMI categories according to the World Health Organization standards, using standard deviations (SD) scores above World Health Organization growth standard median (class 1: 2-3 SD scores above; class 2: >3 SD scores above; class 3: >4 SD scores above). The patients were also assessed by the EOSS-P (stages 0, 1, and 2/3). The goal of this study was to examine the association between BMI class and EOSS-P stage.

The cross-sectional study enrolled patients from the Canadian Pediatric Weight Management Registry, a prospective, multicenter cohort study of children treated in weight management centers between May 2013, and October 2017. The children were age 5 to 17 years and all had available BMI data. Health issues related to obesity were obtained from medical records or based on dedicated questionnaires.

The study cohort included 847 children with obesity, including 546 (64%) with severe obesity (BMI class 2 or 3). Of the entire cohort, 678 (80%) were classified as EOSS-P stage 2/3 (indicating clinically significant health concerns), including 85% of patients with class 3 obesity and 76% of patients with class 1 obesity. The remaining 15% of children with class 3 obesity were classified as EOSS-P stage 0 or 1, suggesting low health burden.

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Mental health issues were very common in this population and evident in 435 children, or approximately 50%. The most common concerns were anxiety (23%) and attention-deficit/hyperactivity disorder (12%).

Health issues were also common among patients classified as EOSS-P stage 2/3, including mental health issues (61%) and metabolic health issues (41%). Metabolic health issues were more common in children with higher BMI class, whereas mental issues were equally distributed across the various BMI classes, except for depression, which was more common with class 2 or 3 obesity. Social issues, such as bullying and low household income, were reported in 179 (21%) patients and were more common with increasing BMI class. Similarly, mechanical health issues, found in 86 (10%) children, were also more common with increasing BMI class.

According to the researchers, the data show that health issues, whether physical or mental, were very common among children with obesity, irrespective of BMI class. Participants with class 3 obesity had the greatest health risk. BMI was correlated with social and mechanical health issues, but did not predict mental and metabolic issues as strongly. The investigators suggested that BMI and EOSS-P provide complementary information regarding the health risk associated with obesity.

Among the study limitations, the researchers noted the lack of prognostic validity of the EOSS-P and the risk for greater health issues in this population of children presenting to weight management clinics. They added that some patients had missing data.

“The application of a clinical staging system such as the EOSS-P in addition to BMI classification might better support clinical and administrative decisions,” concluded the investigators.

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Hadjiyannakis S, Ibrahim Q, Li J, et al. Obesity class versus the Edmonton Obesity Staging System for Pediatrics to define health risk in childhood obesity: results from the CANPWR cross-sectional study [published online April 2, 2019]. Lancet Child Adolesc Health. doi:10.1016/S2352-4642(19)30056-2