Potential circadian and circannual rhythm contributions to the obesity epidemic in elementary school age children

Authors: MORENO, JENNETTE - Children'S Nutrition Research Center (CNRC); CROWLEY, STEPHANIE - Rush University Medical Center; ALFANO, CANDICE - University Of Houston; HANNAY, KEVIN - Schreiner University; Thompson, Deborah - Debbe; BARANOWSKI, TOM - Children'S Nutrition Research Center (CNRC)

Submitted to: International Journal of Behavioral Nutrition and Physical Activity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2019
Publication Date: 3/7/2019
Citation: Moreno, J.P., Crowley, S.J., Alfano, C.A., Hannay, K.M., Thompson, D.J., Baranowski, T. 2019. Potential circadian and circannual rhythm contributions to the obesity epidemic in elementary school age children. International Journal of Behavioral Nutrition and Physical Activity. 16:25. https://doi.org/10.1186/s12966-019-0784-7.
DOI: https://doi.org/10.1186/s12966-019-0784-7

Interpretive Summary: Children gain weight at an accelerated rate during summer. These increases in weight contribute to higher rates overweight and obesity among elementary-school children (i.e., approximately 5 to 11 years old in the US). In recent years these increases in summertime weight have been explained as being due to a lack of structure during summer. However, this explanation ignores biological causes underlying the seasonality of children's growth. In this article, the literature regarding seasonal weight gain is reviewed. There is compelling evidence that children's growth occurs seasonally, suggesting environmental changes resulting from earth's orbit around the sun, send signals to the body, resulting in faster weight gain during late summer and early fall. It is hypothesized that during summer, children experience a transition from the school schedule to the summer holiday environment. During summer, bedtimes may be later and less consistent because children do not have to wake up to go to school the next day. In addition, meal times may be shifted later and children may be less active. These behavioral changes may result in a disruption of daily rhythms, contributing to faster than normal weight gain during summer. The combination of normal seasonality in children's weight gain occurring at the same time as children are on summer holiday likely explains accelerated summer weight gain which contributes to the development of obesity among some children during elementary school. Prevention efforts should include the promotion of consistent bedtimes during the school year and summer, limiting eating after the last meal of the day, decreasing light exposure in the evening, providing opportunities for light exposure during the day and reducing exposure to artificial light at night.

Technical Abstract: Children gain weight at an accelerated rate during summer, contributing to increases in the prevalence of overweight and obesity in elementary-school children (i.e., approximately 5 to 11 years old in the US). Int J Behav Nutr Phys Act 14:100, 2017 explained these changes with the "Structured Days Hypothesis" suggesting that environmental changes in structure between the school year and the summer months result in behavioral changes that ultimately lead to accelerated weight gain. The present article explores an alternative explanation, the circadian clock, including the effects of circannual changes and social demands (i.e., social timing resulting from societal demands such as school or work schedules), and implications for seasonal patterns of weight gain. We provide a model for understanding the role circadian and circannual rhythms may play in the development of child obesity, a framework for examining the intersection of behavioral and biological causes of obesity, and encouragement for future research into bio-behavioral causes of obesity in children.