Adjusted body mass index values that, for the first time, accurately reflect the physical makeup of UK children from ethnic minorities have been drawn up by researchers.
Although BMI is the most widely-used measure of obesity in children, they noted that existing “one-size fits all” standards did not provide accurate readings for UK South Asian or black African children.
“This research will give healthcare professionals extra help in making accurate judgements”
But the researchers from St George’s and University College London believe they have now developed a way to adjust BMI values for ethnicity, so that they reflect body fat more accurately.
They have also help create a simple online BMI calculator that also available in order to provide adjustments.
Existing BMI values consistently overestimated body fat in UK children of Black African descent, and consistently underestimated body fat in UK children of South Asian descent, said the researchers.
They said the adjustments, therefore, tended to lower BMI in black African children and to increase BMI in South Asian children.
The findings, published by the International Journal of Obesity, come from a study funded by the British Heart Foundation and the National Institute for Health Research.
The new values are particularly important, given concerns about high levels of childhood obesity in the UK and diabetes risk among the South Asian population, said the researchers from St George’s.
“The more accurate we can be at screening, identifying and monitoring children at an early age the better”
They said it was crucial that accurate assessments of body fat in children from different ethnic backgrounds were made to prevent, diagnose and manage the wider problem of obesity.
To come up with the necessary BMI adjustments, the researchers looked at four recent UK-based studies that made precise measurements of body fat in 1,725 children aged four to 12 years.
The relationship between BMI and body fatness was explored in each ethnic group and compared to the BMI-body fatness relationship in white children, to derive the necessary BMI adjustments for South Asians and Black Africans.
The study authors found BMI consistently underestimated body fatness in South Asians, requiring positive BMI adjustments of +1.12 kg/m2 for boys and +1.07 kg/m2 for girls of all age groups.
Meanwhile, BMI overestimated body fatness in black Africans, requiring negative BMI adjustments for black African children.
However, these were “complex” because there were statistically significant interactions between black African ethnicity, fatness and age group.
As a result, BMI adjustments varied by age group and fatness level – the largest were in younger children with higher unadjusted BMI and the smallest in older children with lower unadjusted BMI.
Mohammed Hudda, research fellow in medical statistics at St George’s, said: “Childhood obesity is a major public health challenge in the UK.
“This research will give healthcare professionals extra help in making accurate judgements when deciding whether children, particularly of South Asian or black African origin, are underweight, normal, overweight or very overweight (obese),” she said.
Accurate BMI checks for ethnic children for first time
“Of about 3.3 million children of compulsory school age in state-funded primary education, approximately 275,000 are of South Asian ethnic origin and 170,000 of African origin, demonstrating the large number of children in the UK for whom these adjustments would be relevant,” he noted.
Victoria Taylor, heart health dietician at the British Heart Foundation, added: “Childhood obesity tends to track into adulthood, so the more accurate we can be at screening, identifying and monitoring children at an early age the better.
“This exciting research could allow parents and children to be given more accurate information needed to help guide their diet and lifestyle choices as early as possible,” she said.