Indicators of sedentary lifestyle, such as screen time and the presence of a TV in the child's bedroom, were associated with overweight and obesity in Norwegian schoolchildren. Higher parental education was generally associated with less obesogenic lifestyle.

Objectives: The purpose of this study was to investigate the association between weight-related anthropometric measures and children's eating habits, physical activity and sedentary lifestyle at a population level. Methods: Data from the Bergen Growth Study were used to study the association of z-scores of waist circumference (WC), weight-to-height ratio (WHtR), subscapularis (SSF) and triceps (TSF) skinfolds and BMI, with lifestyle factors in 3063 Norwegian children (1543 boys) aged 4-15 years, using linear regression analysis. Each sex was analyzed separately. Results: In a fully adjusted model with additional correction for BMI z-scores, the consumption of vegetables was associated with higher WC (b = 0.03) and TSF (b = 0.05) z-scores in girls. Sedentary behavior was not associated with any of the anthropometric measures. Physical activity was negatively associated with SSF (b = −0.07) and TSF (b = −0.07) z-scores in boys, while a significant negative association was observed with WC (b = −0.02), WHtR (b = −0.03), SSF (b = −0.04) and TSF (b = −0.06) in girls. Conclusion: Physical activity was negatively associated with skinfolds in both sexes. The BMI was not related to the level of physical activity, and should be complemented with direct measures of fat tissue, like skinfolds, when studying the effect of physical activity on body composition in children.

Current Belgian and Norwegian growth references for length/height were found to be largely unaffected by the current proportion of overweight and obese children. There is, therefore, no need for revised height charts that exclude overweight or obese children.

Aim To study how sociodemographic factors and family structure associate with baseline BMI z‐scores (BMIz) and BMIz change in 767 Norwegian children aged 6‐15 years. Methods Baseline BMIz and 1‐year BMIz increments in children from the Bergen Growth Study were analysed with linear and logistic regression, according to sociodemographic factors and family structure. A blended family was defined as including a step‐parent and/or half‐sibling. Results In a fully adjusted regression model, baseline BMIz were only significantly associated with maternal BMI (b = 0.087, 95%CI 0.067, 0.107). Body Mass Index z‐scores increments were larger in children living in a blended family (b = 0.060, 95%CI 0.006, 0.115), with a lower parental education (b = 0.127, 95%CI 0.029, 0.226) and with a higher maternal BMI (b = 0.008, 95%CI 0.001, 0.014). The odds for a large BMIz increment (>1 SD) were higher in children living in blended families (OR 1.82, 95%CI 1.16, 2.88) and with higher maternal BMI (OR 1.07, 95%CI 1.01, 1.13) and lower in 9‐11‐year‐old children (OR 0.44, 95%CI 0.26, 0.77) compared with 12‐15‐year‐olds. Conclusion Body Mass Index z‐scores increments were more strongly associated with sociodemographic factors and living in a blended family than baseline BMIz values. BMI z‐scores increments could be useful for identifying children at risk of becoming overweight or obese.