Seasonal variability in body mass index, waist circumference, and skinfolds in Norwegian children.

Abstract

Studies have shown that children develop a higher body weight during summer months. This has been demonstrated repeatedly using the body mass index (BMI), but the effect of season on other weight-related anthropometric measurements is still unclear. Measurements of height, weight, waist circumference (WC), triceps, and subscapular skinfolds (TSF and SSF), collected from September till May in a cross-sectional sample of 4-16-year-old children and adolescents (n = 4525) from the Bergen Growth Study 1 (BGS1). Differences in z-score by season were tested with linear models adjusted for age group and separately for sex. Overall differences were tested with a one-way between-group analysis of variance. The girls had higher BMIz (+0.12, p = .03) and WCz (+0.18, p = .002) in fall compared with spring. TSFz (-0.19, p < .001) and SSFz (-0.18, p < .001) were lower in winter in girls, and in boys both in fall (TSFz -0.10, p = .046; SSFz - 0.16, p < .001), and winter (TSFz -0.15, p = .004; SSFz -0.14, p = .003), when compared with spring. Seasonal variation was detected for all anthropometric measures, but differences in the direction of the effect between measures of global (BMI), central (WC) or subcutaneous (SF) adiposity suggest a more complex mechanism that needs further exploration.