23rd Feb 2024

Introduction: Optimal time distribution between physical activity, sedentary behaviors, and sleep appears to be essential in obesity management strategies. However, the impact of reallocating time among these behaviors, collectively known as 24-hour movement behaviors, remains underexplored. This study examines the theoretical effects of reallocating time between 24-hour movement behaviors on obesity indicators across different age groups.
Methods: We performed a pooled data meta-analysis of 9,818 participants from 11 observational studies. To estimate the time spent in movement behaviors, we reprocessed and harmonized individual-level raw accelerometer-derived data. Mixed-model compositional regression and isotemporal substitution models estimated theoretical changes in body mass index (BMI) and waist circumference (WC) associated with time reallocation between moderate-to-vigorous physical activity (MVPA), light-intensity physical activity (LPA), sedentary behaviors, and sleep. We performed the analysis separately for children, adolescents, adults, and older adults, and adjusted all models for sex, age, and socioeconomic status.
Results: Significant changes in the obesity indicators were observed even with 10-minute reallocations and become more clinically relevant when 60 minutes were reallocated. The greatest increases in BMI and WC were found when MVPA was reallocated to other movement behaviors, while increasing MVPA was the best protection against obesity. The highest magnitude of the decrease in obesity indicators was observed when time spent in sedentary behavior was substituted with other behaviors. Reallocating time away from sleep and LPA showed several significant changes, but no consistent pattern was observed. Although most of the changes in BMI and WC appeared uniform across different age groups, there were some inconsistent results specifically in adolescents.
Conclusions: This investigation emphasizes the crucial role of MVPA in mitigating obesity risk across the lifespan. The findings also highlight the importance of substituting sedentary behavior with low-intensity movement behaviors, a lifestyle change that can be feasible and sustainable for many people, including those with severe obesity. Inconsistent findings in adolescents may indicate the need to design tailored lifestyle interventions in this age group.