Body mass index and obesity in children with cerebral palsy.

Abstract

This commentary is on the original article by Duran et al. on pages 680–686 of this issue. Childhood obesity has reached endemic proportions over the past 30 years1 and the rate of obesity among children with disabilities has been reported to be even higher. The primary tool used to identify obesity is body mass index (BMI). Defined as the ratio of weight in kilograms divided by the square of height in meters, BMI is used as an inexpensive and widely available surrogate measure of adiposity or fatness. Clearly, BMI is a measure of weight (fat and lean components) in relation to height rather than a direct measure of fatness. Because of changes with growth, BMI is only a moderately sensitive and specific indicator of excess fatness in typically developing children with high BMI2 and determining relative fatness among normal weight children is not possible with BMI alone. BMI in children with cerebral palsy (CP) is even more problematic due to the known inaccuracies of measurement. Critically, obesity in children is strongly associated with negative health consequences; it may also impact physical functioning in those with disabilities. Duran et al.3 report on the performance of BMI to identify excess body fat in children with CP. Their most important finding is the significant number of children with excess fat who have normal weight (and normal BMI). They correctly point out that monitoring only BMI may lead to a failure to identify such children (and dietary management with only an eye on BMI and weight gain can lead to iatrogenic obesity). So where does this leave the clinician? Obesity has been shown to be a significant problem in children and adults with disabilities, with negative impact on health. Importantly, obesity is potentially preventable and modifiable. It is time to go beyond BMI in the care of children with CP. We need to implement valid, reliable tools to better serve patients. Such tools are available and have already been called on.4 Skinfold thickness measurement directly assesses body fatness; it is a simple test that is quick, reliable, and feasible in a clinical context. It requires training and calipers typically used in research are expensive so it has not been widely implemented thus far. Bioelectric impedance and dual-energy X-ray absorptiometry are also validated options, but each with its own limitations. Alternatively, waist-to-hip circumference ratio may be useful, as it has been associated with cardiovascular risk in adults with CP.5 We must implement known methods to identify excess fatness and combine them with tools to measure health, mobility, function, and well-being. Future research must focus on the relationship between fatness and health or function across the lifespan and the development of interventions to improve the health and well-being of those with CP. Otherwise, we may unwittingly contribute to childhood obesity.