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Body mass index (BMI) may not be a suitable measure of body fat for certain ethnicities, researchers suggested.

In an analysis of English schoolchildren, young and adolescent South Asian children had a higher average adjusted BMI compared with age-matched white children, according to an ethnic-specific BMI-adjusted model. Specifically, according to the study online in , Mohammed T. Hudda, MSc, of St. George's, University of London in the U.K., and colleagues found that the BMIs were as follows (P<0.001 for all):

• young males: 16.9, South Asian versus 16.2, white
• young females: 16.8 versus 16.2
• adolescent males: 20.1 versus 18.6
• young females: 19.9 versus 19.0

The BMIs for black young children and adolescents compared with whites were as follows (P<0.001 for all):

• young males: 15.3, black versus 16.2, white
• young females: 15.3 versus 16.2
• adolescent males: 18.4 versus 18.6
• adolescent females: 19.9 versus 19.0

"High [body fatness] in South Asian and black children in England is of particular concern, because both ethnic groups have high risks of [type 2 diabetes] and [cardiovascular disease] in adulthood compared with white children; these risks have their origins in childhood," the authors noted, adding that the typical BMI measure "systemically underestimates [body fatness] in South Asian children and overestimates [body fatness] in black children." As a result, the research group previously developed an in order to reduce such inaccuracies -- the so-called adjusted BMI for English, South Asian, and black children had the same relation to total body fat as in white children.

Drawing on the National Child Measurement Programme, the analysis included 3,195,323 schoolchildren between the ages of 4 and 5, as well as 2,962,673 children between the ages of 10 and 11 from 2007 to 2008.

White children included children identified as White British, White Irish, or any other White background on school or medical records. Black children included Black African, Black Caribbean, or any other Black background. South Asian children included Indian, Pakistani, and Bangladeshi backgrounds, while Other Asian children included Chinese or other Asian origins.

When analyzed across all subgroups, boys and girls of both age groups for each South Asian sub-ethnic group had higher mean adjusted BMIs compared with age- and sex-matched white children (P<0.001 for all). The highest adjusted BMI levels were seen among Bangladeshi children for both age groups, while the lowest was seen among Indian children.

Similar heterogeneity was seen among black children, with 4- to 5-year-old African children reporting a slightly higher adjusted BMI compared with other subgroups.

Between 2007-2008 and 2012-2013, changes in mean adjusted BMI did not differ significantly among black or South Asian boys, although white boys did have a reduction (-0.04, P<0.001). However, black and South Asian girls showed a slight increase in adjusted BMI over this 5-year period (0.06, P=0.003; 0.04, P=0.006, respectively).

Among the 10- to 11-year-old children, black and South Asian boys both had an increase in adjusted BMI over the 5-year period (0.13, P=0.001; 0.16, P<0.001, respectively). All female ethnicities experienced an increase in adjusted BMI, with South Asian girls showing the largest change (white 0.11, black 0.15, South Asian 0.32; P<0.001 for all).

In regards to obesity, South Asian children had the largest prevalence of 4- to 5-year-olds with obesity (39.3% of boys; 33.7% of girls), while black children had the lowest prevalence of obesity (10.2% of boys, 12.2% of girls), with white children in between (24.0% of boys, 21.2% of girls).

A similar pattern of prevalence rates were reported among the 10- to 11-year-old group, except for black girls:

• South Asian: 49.6% of boys; 40.1% of girls
• White: 32.8% of boys; 29.6% of girls
• Black: 31.5% of boys; 33.4% of girls

"The size of the BMI differences observed is sufficiently large to be of substantial public health importance," Hudda and colleagues wrote. "These findings emphasize the particular need for early overweight-obesity prevention in South Asian children, in whom the burdens of high [body fatness] are very high."

Click for the American Association of Clinical Endocrinologists' clinical practice guidelines for the medical care of patients with obesity.

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