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Arnold School of Public Health

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Glenn Weaver investigates when and why children gain weight during school breaks

March 22, 2024 | Erin Bluvas,

With his fourth R01 grant awarded in three years, Glenn Weaver will continue his deep dive into the reasons for and ways to combat BMI increases among children. Funded with $3.5 million from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the exercise science associate professor will be looking for patterns of weight gains and BMI increases based on behavioral, social, environmental and biological factors.

Researchers, including Weaver, have established that the May-August break from school contributes to accelerated BMI gains and increasing rates of childhood obesity – which surpassed 20 percent among children ages six to 11 in 2020. The “Summer Slide” is an area of expertise for Weaver, who not only studies this trend but is also developing programming to reverse the health and academic losses that disproportionately affect underserved groups.

Key Fact


Obesity prevalence was 20.7 percent among six- to 11-year-olds in 2020. 

Weaver is already using $9 million in funding across his three other National Institutes of Health grants to investigate various aspects of this challenge. One project assesses the accuracy of activity trackers in measuring exercise and sleep among children. Another tests the effectiveness of the programming Weaver and his team have created to prevent the effects of the summer slide. A third increases access to summer and after-school programming for children from low-income households.

With this latest grant, Weaver will complete another piece of the puzzle. His team will investigate answers to two questions. The first relates to when these regressions take place. Is it summer only, as circadian rhythms suggest? Or is the structured days hypothesis the most likely explanation?

Based on the work of Weaver and other exercise science faculty, the structured days hypothesis suggests that children’s health behaviors (e.g., active vs sedentary/screen time, dietary intake, sleep) are beneficially regulated by structure, such as the school day or camp programming offered during the summer break.

Glenn Weaver
Glenn Weaver is an associate professor of exercise science, whose work focuses on childhood obesity prevention.

Beyond confirming the root causes for accelerated BMI gain, this study will also examine whether this is solely a summer challenge or if other breaks (spring, winter, fall, etc.) are also to blame for health declines.

“This is a critical limitation in our understanding of when childhood obesity occurs and how to treat it,” says Weaver, who is a faculty affiliate with the Arnold Childhood Obesity Initiative and the Research Center for Child Well-Being.

The research team will recruit three cohorts (3K, Kindergarten, Second grade) of 200 children each to participate in the study. Over the course of three years, they will collect information related to physical activity, sedentary/screen time, dietary intake and sleep as well as social, environmental and biological data.

“Little is known about monthly patterns in BMI change and associated obesogenic behaviors, the dynamic relationship of these behaviors with one another, the social, environmental, and biological determinates of these behaviors, and their link with changes in BMI in children,” Weaver says. “This study will be the first to investigate these areas and has the potential to uncover developmentally sensitive periods when children are susceptible to becoming obese and can provide insight into mechanisms for change.”

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