South Asian children living in the UK have higher average levels of body fat than white European and black African Caribbean children in the UK. The findings show that body mass index (BMI), the most widely used tool to measure body composition, underestimated their body fat, and add to doubts about its use as a measure.

These findings have been made by researchers at St George’s, University of London, and published online in the International Journal of Epidemiology. The researchers say they could aid the development of strategies to combat rising obesity and diabetes levels in the UK South Asian population.

The team used several methods to measure the body fat of 5,758 children from different ethnic groups aged nine and 10 years in London, Birmingham and Leicester. They measured skinfold thickness and bioimpedance – a method for measuring body composition based on the electrical resistance of body tissues – as well as BMI. Skinfold thickness and bioimpedance are more direct measures of body fat content than BMI.

South Asian children had higher average levels of skinfold thickness and fat mass – measured by bioimpedance – than white Europeans, by about five per cent and six per cent, respectively; levels in black African-Caribbeans were similar to or lower than those in white Europeans. However, these ethnic differences were not reflected by BMI differences – average BMI was two per cent lower in South Asians and almost six percent higher in black African-Caribbeans compared with white Europeans. 

“These findings will give policy makers a better understanding of the health problems facing ethnic minority groups. They suggest that preventing UK South Asian children becoming overweight is an important priority,” said Claire Nightingale of the St George’s Division of Population Health Sciences and Education, who led the research. “They also suggest that BMI can be misleading when comparing body fat patterns in children from different ethnic groups – better measures are needed for making such comparisons.”

Increased rates of overweight and obesity in children have been a major public health concern during the last two decades. However, few studies have provided accurate estimates of overall body fat patterns in UK children from different ethnic groups. Those studies which have been carried out used body mass index.

Body fat is an important risk factor for type 2 diabetes and cardiovascular disease. Increased levels of body fat among UK South Asian children is a particular concern because risks of type 2 diabetes and cardiovascular disease are high in that population. Type 2 diabetes is increasingly affecting younger people.

The results are from the Child Heart And Health Study in England (CHASE), which has been studying the health of British children aged nine and 10 years. The research was jointly funded by the Wellcome Trust and the National Prevention Research Initiative.