An interview with Mohammed Hudda, a research fellow in CLAHRC South London’s diabetes theme, who was recently awarded the Sam Ramaiah award for his research on ethnic inequalities in public health. Mohammed is a PhD student in the Population Health Research Institute, St George’s, University of London.
Mohammed, what prompted your interest in studying ethnic inequalities in public health?
The issue of childhood obesity has always struck me as one of the major public health challenges which needs to be addressed, which led me to my research within this area. The rates of childhood overweight and obesity have increased over time, so that together they now affect almost a third of all children aged 2-15 years. Research has shown that being overweight or obese in childhood is associated with a high risk of being overweight or obese in adulthood, which in turn is strongly related to increased type 2 diabetes (T2D) and cardiovascular disease (CVD) risks. Therefore it is crucial to the effective monitoring and prevention of childhood obesity (and its related risks in the short and long term) that we ensure the assessment of childhood overweight and obesity is done accurately.
What health issue does your research address? Why is this research needed?
Body mass index (BMI; weight/height2) is widely used to assess body fat in children. Despite its widespread use, BMI provides inaccurate assessment of childhood body fat levels, particularly in children, for several reasons. Firstly, as it is based on weight, it does not discriminate between the two components of weight; fat and lean mass, which can vary substantially between individuals with the same BMI. Secondly, the standardisation of weight provided by height2 is poor in children, which results in taller children having a higher BMI. Third, childhood BMI does not provide a consistent assessment of body fat in children of different ethnic origins. Research by us and others has shown that it overestimates body fat levels in children of black African descent and underestimates it in children of South Asian origins, compared to their White peers. Taking account of the serious limitations of BMI as a measure of body fat in children, our research has focussed on finding better ways of using weight and height as a measure of body fat in children. This is essential to the effective monitoring and prevention of childhood obesity in the population.
How did you carry out your research?
The research was carried out in two stages, building on data from earlier studies which had made reference standard measurements of body fat in UK children of different ethnic origins. An important first step was to improve the assessment of body fat in children of different ethnic origins by deriving BMI adjustments for children of South Asian and black African origins to ensure the relationship between BMI and body fat is consistent to that of white Europeans (see: Body mass index adjustments to increase the validity of body fatness assessment in UK Black African and South Asian children). However, this approach did not tackle the other limitations of BMI, such as the poor height standardisation or the limited ability to discriminate between fat and lean mass. Our most recent research, published recently in the BMJ, proposes an alternative method for assessing body fat in British children aged 4-15 years based primarily on height and weight measurements. We derived a prediction equation which uses height, weight, sex, age and ethnicity (if available) to estimate childhood lean mass (which can then be subtracted from weight to estimate fat mass). This worked well in children of different ethnic origins.
What were the research findings and what conclusions did you draw?
We tested the ability of the derived equation in a number of ways, including within an independent dataset where we found that it estimated fat levels accurately. This approach provides a more direct method of estimating body fat in the childhood population without the need for more complex forms of assessments like dual energy x-ray absorptiometry (DXA) and magnetic resonance imaging (MRI). It could improve the accuracy of assessments for body fat in children (compared with those provided by BMI) to allow for more effective surveillance, prevention, and management of childhood obesity.
How would you like to see this research taken up by policymakers?
The BMI adjustments could help to improve the assessment of body fat, overweight and obesity in children of ethnic minority origins. An important next step for the prediction equations will be to explore how well the fat mass predictions are related to the development of obesity-related complications (such as type 2 diabetes), compared with conventional assessments, particularly BMI. If stronger associations are observed between childhood body fat and poorer health outcomes, compared to the respective BMI associations, this would suggest that the assessment of childhood body fat would be advantageous over current practice. Our derived equation would therefore provide an accurate method for obtaining such estimates based on routinely available measurements.
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