Overweight and obesity in Norwegian children. Trends, current prevalence, effect of socio-demographic factors and parental perception

Abstract

Background: The prevalence of paediatric overweight and obesity has shown a rapid increase in most parts of the world during the last decades. Estimates of prevalence of overweight and obesity in Norwegian children have been limited, and few studies have explored possible socio-demographic risk factors. The ability of parents to recognize weight deviations in their children is important for the management of emerging weight problems in children. Objectives: To provide new data on weight-for-height and skinfolds in Norwegian children, and compare these to growth references collected in 1971-4. Also, to estimate the prevalence of overweight and obesity by comparisons with the World Health Organization (WHO) growth standard and the International Obesity Task Force (IOTF) criteria for overweight and obesity, and to identify socio-demographic risk factors. Finally, to compare parental perception of their children’s weight status to objective criteria of overweight and underweight based on anthropometric measures (BMI, waist circumference and triceps skinfold thickness). Materials and methods: A total of 8299 children aged 0-21 years from a stratified randomized selection of well-baby centres, kindergartens and schools in the city of Bergen, were included into the Bergen Growth Study during 2003-6. In 2006-7, a parental questionnaire including data on socio-demographic factors and parental perception were sent to 7472 participants and answers obtained for 4905 children. Results: The first paper demonstrated an increase in the weight-for-height, triceps and subscapularis skinfolds between 1971-4 and 2003-6 in 4115 Norwegian children aged 4-15 years. The upward percentile shift was largest in the highest percentiles and more prominent for skinfolds than for weight-for-height. Overall, 18.0% of the boys and 20.1% of the girls were above the 90th weight-for-height percentile of the 1971-4 references. Corresponding values for the triceps skinfolds were 30.0% and 28.0%, and for subscapularis skinfolds 26.5% and 25.9%. In the second paper, the growth of 2231 Norwegian and 4754 Belgian children aged 0- 5 years was compared with the WHO growth standard. In general, the number of Norwegian and Belgian children below – 2 SD of the WHO standards was lower, and the number above + 2 SD higher than was to be expected if there were no differences between the populations. For BMI, the overall percentage below – 2 SD was 0.54% (expected 2.3%) and 4.29% above the + 2 SD (expected 2.3%). This was true for all Norwegian children, also those who were exclusively breastfed. The results were similar for the Belgian children. The third paper reported the prevalence of overweight and obesity as defined by the IOTF in 6386 healthy Norwegian children aged 2-19 years. Overall 13.8% were assigned as overweight and 2.3% as obese. The prevalence was highest in the primaryschool aged children (17.0%) as compared to pre-school children (12.7%) and adolescents (11.7%). Significantly more girls than boys were overweight in the preschool age group (15.8% in girls vs. 9.6% in boys, p<0.001), whereas the opposite was true for adolescents (12.9% in boys vs. 10.2% in girls, p=0.026). Furthermore, this paper described the effect of socio-demographic risk factors on the prevalence of overweight and obesity as explored in a subsample of 3793 children. The risk of being overweight or obese increased in children with fewer siblings (p=0.003) and with lower parental educational level (p=0.001). No association was found with parental employment status, single-parent families or ethnic origin. The fourth paper showed that 71.2% of overweight and obese children and 40.8% of underweight children, using the IOTF definition for overweight and a similar criterion for underweight, were recognised by their parents as being of normal weight. Above 90% of overweight pre-school children were assigned as normal weight. For a given value of BMI, primary-school age children, adolescents and girls had an increased risk of being assigned as overweight, whereas adolescents and girls had a lower risk of being assigned as underweight. Overweight parents more often assigned their children as underweight, but there was no effect of parental educational level or parental underweight. Conclusions: There has been a significant increase in weight-for-height in Norwegian children during the last 30 years, and the increase in skinfolds indicate that increase in fat tissue is responsible for these changes. The current prevalence of overweight and obesity is comparable with data from other North- and Western-European countries, but lower than seen in Southern-Europe, the UK and the US. Socio-demographic factors have marked effects on the current prevalence of overweight and obesity. It is of great concern that in light of the increased prevalence of childhood overweight, parental ability to recognize weight deviations in their offspring is generally poor.