BMI may underestimate true extent of childhood obesity problem study reveals
The study, led by Senior lecturer Claire Griffiths, with childhood obesity expert Professor Paul Gately, Dr Paul Marchant and Professor Carlton Cooke in collaboration with Leeds City Council, compared BMI, waist circumference (WC) and waist-to-height ratio (WHtR) data in 14,697 Leeds school children over three years. The results are consistent with reports of a levelling off in overweight and obesity in children of a similar age according to BMI. However, the results also show that the prevalence of central obesity, measured by WC, is considerably higher than estimates based on BMI, especially in girls.
6% of boys and 15% of girls would not have been identified as being at increased risk based on BMI measurement alone. What is most shocking is that at age eleven, over 2000 girls in Leeds exceeded the WC cut point for increased risk in female adults (80cm). Again, this is information that would not have been detected using BMI alone. It is not yet possible to estimate the impact of the increase in WC on current and future health risk but the increases should be of concern based on recent research showing the link between waist circumference and risk of Type 2 Diabetes*.
Ms Griffiths commented: "Although the choice of BMI as a measure of obesity in children is well-established, and even recommended, widespread use of BMI to assess fatness in children may conceal differences in body composition and central adiposity which potentially pose a greater health risk. Conclusions linking BMI, WC and WHtR as measures of obesity to health risk in children cannot be drawn from the data; however the data could have serious implications for public health, suggesting that there is a need to understand the relationship between BMI and WC, with growth and health risk."
This study is important as it highlights the health risks to 429 boys and 992 girls who would have been missed by using BMI alone. The study also demonstrates the strong collaboration between Leeds Metropolitan University and Leeds City Council and the proactive approach to public health which they have established in Leeds.
The study is part of an annual programme Leeds Metropolitan University carries out in partnership with Leeds City Council called the Rugby League and Athletics Development Scheme (RADS), which has been running for several years. Through working with secondary schools in Leeds collecting data on a range of sports performance skills as well as height, weight, BMI and waist circumference, the council and its partners are able to effectively target of a range of anti-obesity activities in the city as well as plan targeted interventions. The research also enables schools to actively influence the health and educational activities within schools.
*The InterAct Consortium (2012) Long-Term Risk of Incident Type 2 Diabetes and Measures of Overall and Regional Obesity: The EPIC-InterAct Case-Cohort Study. PLoS Med 9(6): e1001230. doi:10.1371/journal.pmed.1001230