Child Growth Study 2008 Results (adjusted for light clothing)
About 17 per cent of girls and 14 per cent of boys in third grade are defined as overweight. Of these, a smaller proportion is obese. The data are obtained from the "Child Growth Study in Norway", which was conducted in autumn 2008. The prevalence of overweight and obesity is significantly lower in Norway than in Britain and the United States.
In the third grade in Norway, children are eight to nine years old.
The results were published in a report in the following spring and in 2010, the researchers adjusted the data from the report to account for the children wearing light clothing during weighing. Here is a summary of the findings in English.
These figures were adjusted for light clothing:
- The total proportion of overweight or obese: 17 per cent for girls and 14 per cent for boys.
- The proportion of overweight: 13 per cent for girls and 11 per cent for boys.
- The difference between girls and boys is thus statistically significant.
- The proportion of obesity: between 3.5 and 4 per cent for both boys and girls, (not statistically significant).
Other results :
- On average in the third grade, girls are 131 cm and boys are 133 cm tall.
- The average weight is 29.1 kg and 29.7 kg for girls and boys respectively.
- On average, body mass index (BMI) is 16.8 kg/m2 for both girls and boys.
|Figure 1: Overweight and obesity among 8-9 year olds, 2008. Classified by IOTF definitions and corrected for light clothing. Significance 0.021|
Differences between the health regions
For each health region, the changes in the adjusted numbers are small, see tables and figures below. Overall, the proportion of overweight and obesity varies by 6.4 per cent between the regions, the differences are not greater than one would expect in such a study. Random variations will occur.
|Figure 2: Percentage of girls (top) and boys with overweight and obesity in Norway and in the different health regions, calculated according to the Cole index. The figures are adjusted for light clothing. The difference between the regions is not statistically significant. Source: Department of Health Statistics, NIPH.|
|Overweight and obesity %||Obesity %||Overweight %||High waist circumference %|
|Norway total (127 schools)||17*||3.9||13||9|
|Health Region South East||15||3.0||12||8|
|Health Region West||19||5.1||14||10|
|Health Region Mid-Central||18||4.4||14||8|
|Health Region North||21||5.5||16||11|
|Norway total (127 schools)||14||3.4||11||7|
|Health Region South East||12||3.3||9||7|
|Health Region West||14||2.7||11||6|
|Health Region Mid-Central||19||4.4||15||10|
|Health Region North||16||3.8||12||10|
* Significance 0.021
Difference between boys and girls
The results show that the proportion of girls with overweight and obesity is about two percentage points higher than among boys of the same age. This may be a coincidence because there is a selection of girls and boys who have been measured. Waist-to-height ratio is also slightly higher among girls than among boys (see below). Overall, this suggests that among 8-9 year-old girls there is a slightly higher proportion of overweight and obesity than among 8-9 year old boys, see Figure 3.
The 2010 study will provide more information about gender differences.
|Figure 3: Percentage of boys and girls with overweight (excluding obesity), high waist circumference and obesity. Left: overweight classified by Cole index. Middle: high waist circumference – waist-to-height ratio is 0.5 or higher. Right: obesity. Source: Department of Health Statistics, NIPH|
Difficult to comment on trends
Ragnhild Hovengen is the Project Manager for the Child Growth Study.
Can you conclude from this study that many Norwegian children are overweight?
"There are very few other studies for comparison. The Norwegian School of Sport Sciences made a similar study of 9 year-olds in 2005-2006. This showed similar results for 9 year-olds, that 16 per cent of boys and 19 per cent of the girls were overweight / obese. The situation has not changed since 2005-2006."
What was the situation 20-30 years ago?
"For adults, we have data showing that a greater proportion is overweight or obese now than 20-30 years ago. The trend is alarming. For children we have little data for comparison. We have no nationwide studies with objective measurements before 2005. A local study from Bergen confirms a general impression that a larger proportion of children are overweight now than 35 years ago."
It's not so long since all children were weighed and measured by the school health service?
"These data were not systematic. They exist as a collection of archive index cards that have not been compiled, and therefore do not provide information about developments in the Norwegian child population. The general impression is that more children are overweight now than a few decades ago, based on what we see around us, photographs and observations of health care professionals. But we have little data to confirm this impression, to measure how big the changes are, when they started and whether the trend is continuing."
Fewer obese children in Norway than in USA and UK
How large is the proportion of overweight children in Norway compared with other countries?
"The countries we have most data from are the UK and USA. In these two countries a total of around 35 per cent of children are overweight or obese. This is twice the proportion in Norway. There are few studies from other countries, in which a representative sample of children is weighed and measured and followed over time. New figures from France and USA suggest that the proportion of overweight children is no longer increasing.
With the Child Growth Study in Norway and similar studies in other European countries, the WHO is hoping to fill this knowledge gap. At the Norwegian Institute of Public Health, we are very keen to follow up with more studies. We do not know if the trend in Norway is increasing or levelling out. In addition to conducting a Child Growth Study of new third graders every other year, we also want to follow up the 2008 cohort in the seventh and tenth grade."
Uncertain which overweight children become overweight adults
Is an 8-9-year-old with "overweight" or "obesity" doomed to be overweight or obese in adulthood?
"We know that the risk is higher for overweight than normal weight children, but we also know that many people grow out of those extra kilos. Here we have a great need for more knowledge. We are interested in knowing whether there is a "critical age" that provides information on overweight risk in adulthood. We are also interested in knowing more about the importance of weight and waist circumference for child health and weight development. Moreover, we need more knowledge about the difference between girls and boys," said Hovengen who has completed data collection for the 2010 study among third graders.