Health | Child obesity study finds the most vulnerable age is 9 or 10

A study on obesity rates in children, co-produced by a Macau-based scholar, recently found that the age group 9 to 10 years old is a “critical period” in understanding the obesity epidemic afflicting much of the developed world.

A partnership of five scholars from universities based out of South Africa, Portugal, mainland China, Hong Kong and Macau, the study sampled more than 10,000 students for six years, tracking the differences in the obesity rate each year. Of this figure, approximately 900 students were tested from Macau between 2008 and 2013.

At the beginning of the study, when the participants were aged 6, the proportion of Macau students considered obese stood at 6.9 percent, while a further 10.8 percent were considered overweight. Only a half-decade later, those proportions had jumped to 13.1 percent and 12.9 percent respectively.

This indicates that obesity rates are prone to suddenly increase at some point during ages 6 and 11.

“There is evidence that rapid weight gain during the first years of life is associated with being overweight later in life. Therefore, overweight tendencies need to be detected at an appropriate age, and suitable strategies need to be implemented for weight management to achieve optimal long-term health,” argued the report’s authors.

According to one of them, University of Macau assistant professor Walter King, “all over the world, students are gradually increasing in weight [disproportionate to what is considered normal], but ages 9 to 10 appears to be a critical period.”

“The same group of students were monitored [throughout the survey] for six years, tracking the differences in the obesity rate [each year],” he explained yesterday in an interview with the Times. “The point was not to determine that the obesity rate has risen – we know that this is happening. We know that there is a sudden increase at a particular age group and we wanted to find out what that age group was.”

The study used Body Mass Index (BMI), a measure of body fat based on height and weight proportions, to determine whether the child participants could be classified as underweight, standard weight, overweight or obese. BMI, which is principally used for adults, can produce distortive effects when applied to children if their age and gender are not taken into account.

However, the authors advance that “overweight or obesity is easily observed when there is an increase in weight without an increase of height.”

According to the study, “BMI was calculated as the primary variable […] and was designated as the weight in kilograms divided by the height in meters squared (kg/m2).”

King accepted that further studies were needed to arrive at a more confident conclusion.

“It is important to note that this is just a small sample size of 900, but more data is coming from a recent study of around 15,000 students from various cities around the world […] such as Seoul and Hong Kong,” the UM scholar noted.

He said that if the data from the latest study corroborates the findings published in the report, then “we can say it’s a universal phenomenon for this age group.”

Asked what might be the cause behind the sudden increase in obesity rates at this age, King preferred not to speculate, adding “we have no other information [than that published in the article].”

However, he advised that “we need to do more to adopt intervention projects, like those that the DSEJ [Education and Youth Affairs Bureau] is currently implementing, to promote physical exercise in schools.”