Seasonality of children's height and weight and their contribution to accelerated summer weight gain

Authors: MORENO, JENNETTE - Children'S Nutrition Research Center (CNRC); MUSAAD, SALMA - Children'S Nutrition Research Center (CNRC); DADABHOY, HAFZA - Children'S Nutrition Research Center (CNRC); BARANOWSKI, TOM - Children'S Nutrition Research Center (CNRC); CROWLEY, STEPHANIE - Rush University Medical Center; Thompson, Deborah - Debbe; CHEN, TZUAN - University Of Houston; JOHNSTON, CRAIG - University Of Houston

Submitted to: Frontiers in Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2022
Publication Date: 5/10/2022
Citation: Moreno, J.P., Musaad, S., Dadabhoy, H., Baranowski, T., Crowley, S.J., Thompson, D.J., Chen, T.A., Johnston, C.A. 2022. Seasonality of children's height and weight and their contribution to accelerated summer weight gain. Frontiers in Physiology. 13. Article 793999. https://doi.org/10.3389/fphys.2022.793999.

Interpretive Summary: Although children have been shown to have an increased body mass index (BMI) during the summer compared to the school year, it is unknown if this is due to seasonal changes in height or weight separately. Nurses measured heights and weights in Kindergarteners twice a year from the beginning of kindergarten through 5th grade. Variation in height and weight by season (school year vs summer) was evaluated. The rate of height gain was greater during the school year when compared to summer. The rate of weight gain did not differ seasonally. Height gain was more strongly associated with increased BMI during summer compared to the school year, mainly among children who remained a healthy weight throughout elementary school and those who transitioned to a healthier weight status. We found a similar seasonal effect for the association between weight with BMI, particularly among children who maintained a healthy weight status. This study indicates seasonality in children's height gain, gaining height at a faster rate during the school year compared to the summer, while weight gain remained relatively consistent throughout the year. Seasonality in height and weight gain had the greatest impact on BMI among children with a healthy weight status. Future research with more frequent measurements is needed to better understand the seasonal regulation of children's growth and weight gain status.

Technical Abstract: While children have been shown to have increased BMI during the summer compared to the school year, it is not known if this may be due to seasonal variations in height or weight separately. Trained nurses measured heights (cm) and weights (kg) in a cohort of Kindergarteners (n=7599) twice per year from the beginning of kindergarten through 5th grade. Variation in height and weight by season (school year vs. summer) was examined using separate mixed-effects models. Season, sex, and BMI trajectory group were tested as 'xed effects. Random effects included repeated measurements of time, students nested within a school, intercept, and slope for growth over time. Similar models using BMIz as the outcome examined the interaction of height or weight with season. The rate of height gain was greater during the school year (~Sept to April) compared to summer (~April to Sept) (Beta=-0.05, SE = 0.013, p<0.0001). The rate of weight gain did not differ seasonally. Height gain was more strongly associated with increased BMIz during summer compared to the school year (Beta=.02, SE = 0.005, p<0.0001), mainly among children who remained healthy weight throughout elementary school (Beta=0.014, SE=0.003, p<0.0001) and those who transitioned to a healthier weight status (Beta=.0.026, SE=0.008, p=0.004). We found a similar seasonal effect for the association between weight with BMIz (Beta=.0.016, SE=0.003, p<0.0001), particularly among children who maintained a healthy weight status (Beta=. 0.014, SE=0.014, p<0.0001). This study indicates seasonality in children's height gain, gaining height at a faster rate during the school year compared to the summer, while weight gain remained relatively more consistent throughout the year. Seasonality in height and weight gain had the greatest impact on BMIz among children with a healthy weight status. Future research with more frequent measurements is needed to better understand the seasonal regulation of children’s growth and weight gain.