Summer vacation is a 3-month window of vulnerability for children from low-income households when health behaviors and academic learning decay. The goal of this project is to collect information on where low-income children go during summer, what they do when they get there, and how their behaviors (physical activity, sedentary, sleep, and diet) differ between the summer (unstructured days) and school year (structured days). This study is 1) significant because it will provide evidence on potential points of intervention that can reduce or reverse the excessive unhealthy weight gains that occur during summer and 2) innovative because it will be the first to identify changes in activity, sedentary, sleep, and dietary behaviors during prolonged and shorter periodic breaks from school and link these behaviors to changes in zBMI over time.

For children (5-12yrs) from low-income households, summer vacation is a "window of vulnerability" and represents an extended period of time (typically 9-10 weeks) in which declines in academic performance occur. For 30 years, empirical evidence has indicated that children from low-income households experience greater declines in reading and math skills during the summer vacation than their middle-to-upper income peers. Additionally, a growing body of evidence demonstrates that the amount of weight gained during summer vacation is 3-5 times greater than the amount of weight gained during the school year. Moreover, this excessive weight gain during summer is more pronounced for low-income, minority children, the same children experiencing the greatest summer learning loss. What children eat and drink, the types of physical activity opportunities, and the amount of screen-time and sleep (two important correlates of weight gain) they engage in during summer vacation is unknown. However, a substantial body of literature indicates that children engage in a greater number of obesogenic behaviors during less-structured times (e.g., weekend days) compared to more-structured times (e.g., week/school days). This phenomenon is refered to as the Structured Days Hypothesis. These behaviors include 1) increased time spent sedentary, 2) reduced engagement in physical activity, 3) displaced sleep patterns, and 4) unhealthy dietary patterns. This study hypothesizes that summer vacation is simply one long weekend where the effect of children's obesogenic behaviors on weight are compounded over a three month time period. However, should children be involved in a structured program over the summer they would not engage in obesogenic behaviors and they would not experience unhealthy weight gains and fitness loss. Recently, one school district in the Columbia, SC area adopted a year-round calendar for an elementary school. This provides a unique opportunity to conduct a natural experiment examining the effects of shorter periodic breaks vs. one prolonged break from structured days (i.e., school days) on the obesogenic behaviors, weight gain, and fitness. This study will use a two arm accelerated longitudinal cohort design to complete the following specific aims: Aim 1: Compare changes in BMI z-scores and fitness during the traditional 3-month summer and 9-month school year between children attending a school that follows a year-round school calendar to children attending match-paired schools that follow a traditional school calendar. Aim 2: Compare changes in sleep, physical activity, sedentary behaviors, and diet during the traditional 3-month summer and 9-month school year between children attending a school that follows a year-round school calendar to children attending match-paired schools that follow a traditional school calendar. This study is significant because the reason for children's weight gain and fitness loss during the summer is unknown. This study is innovative because no studies have examined the effects of prolonged (9 weeks all at once) vs. periodic breaks (3 week breaks distributed throughout the year) from a structured environment on children's weight and fitness.

Inclusion Criteria:

K, 1st, 2nd, and 3rd grade students without any physical and/or medical conditions that would limit their ability to take part in measurements.

Exclusion Criteria:

Children in the 4th and 5th grade will be excluded from participation in the obesogenic behavior assessments because they will move out of elementary school over the two-year study.

Three schools (2 traditional and 1 year-round) enrolling 1,279 students have agreed to participate. 85.0% of children in these schools qualify for free and/or reduced price lunch, and 67.5% of children attending these schools are black, 28.5% are white, and 3.6% are Hispanic. The first school was selected to participate because it operates on a year-round calendar. The second and third schools were selected because their enrollment size and student demographics closely match the enrollment and student demographics of the first school. All children in the participating schools will have their height/weight and cardiovascular fitness measured.