The interplay between lying, sitting, standing, moving, and walking on obesity risk in older adults: A compositional and isotemporal substitution analysis

Introduction : Obesity in older adults is linked to various chronic conditions and decreased quality of life. Traditional physical activity guidelines often overlook the specific postures and movements that older adults engage in daily. This study aims to explore the compositional associations between posture-specific behaviours and obesity risk in younger (M = 67.35 ± 2.03 years) and older (M = 75.73 ± 4.17 years) seniors and investigate the differences in BMI associated with replacing time spent in lying, sitting and standing with moving or walking. Methods : The study involved 309 older adults aged 65 and above from Czech Republic. Participants' movement behaviours, including lying, sitting, standing, moving, and walking, were measured using accelerometers. The data were analysed using compositional data analysis (CoDA) and isotemporal substitution models to assess the impact of reallocating time between different activities on body mass index (BMI). Results : The younger group engaged in more overall movement (193.84 min/day vs. 172.41 min/day) and walking (92.15 min/day vs. 76.62 min/day) than the older group. Significant BMI increases were observed when 30 minutes were reallocated from movement to lying, sitting, or standing (up to +3.306 kg/m²), while reallocating the same amount of time from lying, sitting, or standing to movement led to BMI reductions (up to -2.537 kg/m²). In the older group, reallocating time from slow walking to lying or sitting led to BMI increases (up to +1.855 kg/m²), while increasing time spent slow walking at the expense of lying or sitting reduced BMI (up to -0.949 kg/m²). Conclusions : Promoting movement and walking, particularly slow walking, is crucial in managing obesity risk in older adults. The findings emphasize the importance of reducing sedentary time and encouraging low-intensity physical activity tailored to the capabilities of seniors, especially those aged 70+, to effectively mitigate obesity risk.