Reallocating time between physical activity, sedentary behavior, and sleep for obesity management across the lifespan

Background: Optimal time distribution between physical activity, sedentary behaviors (SB), 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.
Purpose: We estimated the theoretical effects of reallocating time between 24-hour movement behaviors on obesity indicators across different age groups.
Methods: A pooled data meta-analysis of 9,818 participants from 11 observational studies were performed. To estimate the time spent in movement behaviors, we reprocessed and harmonized individual-level raw accelerometer-derived data. The compositional isotemporal substitution models estimated 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), SB, and sleep. We performed the analysis separately for children, adolescents, adults, and older adults.
Results: Significant changes in BMI and WC were observed even with 10-minute reallocations and became more clinically relevant when 60 minutes were reallocated. The greatest increases in obesity indicators 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 BMI and WC was observed when time spent in SB was substituted with other behaviors. Reallocating time away from sleep and LPA showed several significant changes, but no consistent pattern was observed.
Conclusions: This investigation emphasizes the crucial role of MVPA in mitigating obesity risk across the lifespan. The findings also highlight the importance of substituting SB with low-intensity movement behaviors.
Practical implications: This study suggests that even small increases in physical activity and replacing sedentary time can improve weight status across all ages. Such a lifestyle change can be feasible and sustainable for many people, including those with severe obesity.
Funding: Czech Science Foundation (18-09188S and 22-02392S)