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

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