Abstract
Background: Summer weight gain and fitness loss has been identified as a public health concern for children. The objective of this study was to compare changes in weight status and cardiovascular fitness in children attending year-round and traditional calendar schools. Methods: Participants were 321 children from a traditional and year-round school. BMI and Progressive Aerobic Cardiovascular Endurance Run (PACER) Laps were collected during school. Multilevel general linear mixed-effects models were utilized to examine changes in BMI and PACER over the summer while also considering summer camp and sport participation. Results: Children had higher BMI z-scores during Fall 2018 compared with Spring 2018 (b = 0.09, p = 0.006). This effect was modified by Break Length, as students with 3-week (b = -0.09, p = 0.012) and 7-week breaks (b = -0.10, p = 0.003) displayed attenuated increases in BMI z-scores compared with 12-week breaks. For PACER Laps, students who participated in summer sports displayed improvements compared with nonparticipants (b = 4.6 laps, p = 0.001). Conclusions: Shorter summer breaks appear to have a protective effect on summer weight gain when compared with a traditional 12-week break. In addition, children who participated in organized sport over the summer did see a significant improvement in cardiovascular fitness. Schools might consider a year-round school calendar for its potential to protect against summer weight gain.