Fig. 1

Model for Circadian and Circannual Contributions to Children’s weight gain. Figure 1 Footnote. We propose that the individual is nested within their environment which includes the influences of social demands (e.g., social timing resulting from demands such as school or work schedules, social activities, family obligations and routines, parenting practices, community involvement, time zone, etc.), the modern lighting and climate controlled environment, as well as the effect of the earth’s natural environment. Within the individual, there is an interdependence of the circadian clocks, behavior, and health. The major contribution of this model is that the circannual clock interacts with the circadian clocks to promote optimal health and disruption of children’s circannual influences may have health consequences [70]. We propose interactions within the individual and across levels of this model. For example, social demands influence an individual’s behavior which affects alignment of the clocks either by direct entrainment of the peripheral clocks (i.e., meal timing and consistency) or by affecting exposure to the light-dark cycle via sleep timing and consistency, physical activity, and exposure to artificial light at night. It is also proposed that circadian disruption caused by the school holiday may contribute to disruption of circannual rhythms of growth, resulting in accelerated summer weight gain and contributing to the development of overweight and obesity during elementary school. This model was adapted from Roenneberg T, Merrow M. The Circadian Clock and Human Health. Curr Biol. 2016;26(10):R432–443