The impact of summer on obesogenic behaviors and BMI in children with intellectual and developmental disabilities

The National Institute of Child Health and Human Development awarded the University of South Carolina $155,620 on December 1, 2026, under the Child Health and Human Development Extramural Research program (CFDA 93.865) to conduct a longitudinal study examining seasonal changes in obesogenic behaviors and body mass index in children with intellectual and developmental disabilities.

The project investigates how structure—present during the school year but absent during summer—influences weight-related outcomes and behaviors in children with IDD, who face elevated obesity risk compared to typically developing peers. The research examines individual characteristics such as adaptive functioning and physical limitations that may moderate the relationship between seasonal structure and obesity-related changes. The study leverages community relationships and methodology from a parent R01 project to conduct one of the first investigations of longitudinal BMI changes and seasonal differences in children with IDD, comparing obesogenic behaviors between school year and summer periods.

Work is performed in Columbia, South Carolina, with a period of performance from December 1, 2026, through July 14, 2029. The award is classified as a Project Grant.

Abstract

Children with intellectual and developmental disabilities (IDD) are at greater risk of being overweight and obese than their typically developing counterparts. Despite this increased risk, research examining seasonal changes in obesogenic behaviors in children with IDD is minimal, and research examining seasonal changes in body mass index (BMI) is presently unavailable. The structured days hypothesis (SDH) explains how structure in typically developing children plays a protective role against worsening obesogenic behaviors and BMI gains, however, research examining the SDH in children with IDD is limited and findings are not robust. Further, the current studies examining seasonal differences in obesogenic behaviors in children with IDD do not investigate how the unique factors these children possess (e.g., adaptive functioning, physical limitations) can moderate the influence structure has on relationship between season and obesogenic behaviors and BMI. Therefore, we are unable to distinguish when children with IDD are at most risk for worsening obesogenic and accelerated BMI gains and who may benefit the most from the exposure to structure. This project aims to identify when children with IDD are most at risk for worsening obesogenic behaviors and accelerated BMI gain and which individual characteristics influence their response to structure. This project will be one of the first studies to examine longitudinal changes in BMI to investigate seasonal differences in BMI gains in children with IDD. IT will also investigate how obesogenic behaviors differ from the school year to summer, while exploring individual characteristics that may moderate the influence structure has on the relationship between season and obesogenic behaviors. Leveraging the community relationships, methodology, and timeline of the primary R01 project, the proposed F32 project will recruit 40 parent/primary caretakers and child dyads to assess obesogenic behaviors, BMI, and parents' perception of benefits of structure. Obesogenic behaviors will be assessed with both subjective measures (e.g., parent-reported surveys) and objective measures (e.g., accelerometry) during two distinct 14-day timepoints, occurring once during the school year (e.g., march-april) and once during the summer (e.g., june-july). BMI will be measured at three time points: end of spring (~may), end of summer (~august), and again the following spring (~may). Change over summer will be calculated from may to august and change during the school year from august to the following may. This study is significant as IT addresses a critical public health issue in a high-risk population and will yield novel insights into behavioral pathways contributing to BMI increases, as well as how structured environments may mitigate this risk. IT is innovative as IT is among the first to examine seasonal BMI changes between the school year and summer in children with IDD, while accounting for the unique characteristics that may change how structure influences the relationship between season and obesogenic behaviors. Findings will help identify which children benefit most from structure, informing targeted interventions for those at greatest risk.