Changes in Weight, Sedentary Behaviour and Physical Activity during the School Year and Summer Vacation.

Chiaki Tanaka,Shigeho Tanaka,Maki Tanaka,John J Reilly

doi:10.3390/ijerph15050915

Abstract

Background: To examine bidirectional associations between body weight and objectively assessed sedentary behaviour (SB) and physical activity (PA) during the school year and summer vacation. Methods: Participants were 209 Japanese boys and girls (9.0 ± 1.8 years at baseline). SB and PA were measured using triaxial accelerometry that discriminated between ambulatory and non-ambulatory PA, screen time measured by questionnaire during the school-term was evaluated in May and the summer vacation, and relative body weight measured in May and just after the end of summer vacation. Results: There were no significant relationships between changes in SB or PA and changes in body weight. However, higher relative body weight at baseline was associated with decreased non-ambulatory moderate PA (p = 0.049), but this association was slightly diminished after adjusting for change in SB (p = 0.056). Longer screen time at baseline was also associated with increased relative body weight (p = 0.033). Conclusions: The present study revealed that body weight might be particularly influential on non-ambulatory moderate PA while SB, PA or changes in these variables did not predict changes in body weight. Moreover, screen time during the school year is a predictor of change in relative body weight during the subsequent summer vacation.

Highlights

Prevalence of obesity has been decreasing in Japanese children recently according to a national survey [1], but remains much higher compared to 1980 or even 1990 [2]
This review suggested that physical activity (PA) may be the primary factor contributing to these seasonal increases in weight or body mass index (BMI), mainly because some studies indicated a decrease in PA in the summer vacation [3]
Ambulatory and total time in LPA, MVPA, moderate PA (MPA) and vigorous PA (VPA), non-ambulatory time in VPA and step counts significantly decreased from baseline to follow-up

Summary

Introduction

Prevalence of obesity has been decreasing in Japanese children recently according to a national survey [1], but remains much higher compared to 1980 or even 1990 [2]. This review suggested that physical activity (PA) may be the primary factor contributing to these seasonal (summer vacation) increases in weight or BMI, mainly because some studies indicated a decrease in PA in the summer vacation [3]. Results on this issue have been inconsistent, and the cause-effect relationship has not been confirmed [3]. To examine bidirectional associations between body weight and objectively assessed sedentary behaviour (SB) and physical activity (PA) during the school year and summer vacation. Screen time during the school year is a predictor of change in relative body weight during the subsequent summer vacation

Results

Discussion

Conclusion