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BMI Is Ineffective Indicator Of Children’s Health

Posted on: Monday, 30 June 2008, 14:45 CDT

A new British study has found that a child’s body mass index (BMI) does not provide an adequate indication of whether they are meeting exercise goals.   Instead, a simple blood test may be a better method to measure the benefits of exercise in children, the researchers say.

Although BMI measurements have traditionally provided an accurate indication of overall health in adults, there has been debate over its effectiveness in children.

Indeed, the researchers found that using BMI measurements did not distinguish between children who exercised regularly and those who did not. And some experts have suggested that it is possible for children to be both fat and fit, provided they are active enough.

The current study was conducted over a four year time period at Peninsula Medical School in Plymouth, where researchers analyzed the exercise levels of 99 girls and 113 boys born in 1995 and 1996.

All of the children were equipped with accelerometers that measured movement and provided an accurate measure of the amount of daily exercise.

Corroborating what other studies have shown, the researchers found that just over half of the boys and nearly ninety percent of the girls fell short of the "hour a day" goal. But no impact on the relative BMI of the children was observed, despite the variety of different exercise patterns.

Even fat-measuring methods used successfully in adults to predict health levels failed to distinguish children who met the exercise targets from those who did not.

However, the results do not mean that those meeting the target were no healthier than the others. In fact, blood testing revealed clear differences in things such as insulin resistance and cholesterol levels, both of which measure underlying metabolic signs of health.

"BMI just doesn't pick up any differences in children - it's just not a sufficiently sensitive measure,” Professor Terry Wilkin, who led the study, told BBC News.

"And you can't carry out blood testing on this scale in schools."

Wilkin said that even if large amounts of sports were arranged at schools, previous research suggests it is almost impossible to change the overall amount of children’s weekly exercise.

"It could be that changing the diet of children will be the modifiable factor."

Child exercise scientist Dr Richard Winsley told BBC News that in the absence of other practical tests, BMI should still to be used since it still reveals a comprehensive overview of improving or declining fitness levels.

"Whether or not BMI is very good for an individual person may be questionable,” he said.

"But until someone comes up with a more successful, and equally practical alternative, then it is the best we have got," he said, adding that parents and schools should still encourage children to get plenty of exercise. 

"A lack of evidence doesn't mean that something doesn't actually work."

The British government currently recommends that children get an hour of daily moderate to reduce the risk of adult obesity, diabetes and heart disease.

The study was published in the Archives of Disease in Childhood.  An abstract can be viewed at http://adc.bmj.com/cgi/content/abstract/adc.2007.135012v1

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Peninsula Medical School

Source: redorbit Staff & Wire Reports

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