Reallocating 24-hour movement behaviors and cardiometabolic health in adults: a systematic review and meta-analysis

Abstract Background This study examined the associations of reallocating time among 24-hour movement behaviors (24HMB) on cardiometabolic health outcomes (anthropometric indicators, blood pressure, glucose, lipids) in adults. Methods Seven databases (PubMed, Embase, Cochrane Library, ProQuest, Web of Science, CINAHL and SPORTDiscus) were systematically searched through August 2024. Studies were eligible if they assessed the association between 24HMB and cardiometabolic outcomes. Study quality was evaluated using established assessment tools. Meta-analyses were performed when at least three studies provided comparable 30-minute isotemporal substitution estimates for a specific outcome. Results Twenty-one eligible studies (62,056 participants) were included. Reallocating 30-minute of sedentary to moderate-to-vigorous physical activity (MVPA) was associated with lower body mass index (BMI) (β = -0.53, 95% CI -0.81 to -0.26), lower waist circumference (β = -1.42, 95% CI: -2.19 to -0.56), higher high-density lipoprotein cholesterol (β = 0.02, 95% CI: 0.01 to 0.03), and lower triglyceride levels (β = -0.06, 95% CI: -0.11 to -0.01). Replacing sedentary behavior with sleep (β = -0.13, 95% CI -0.19 to -0.07) was associated with lower BMI. Substituting sedentary behavior with either sleep (β = -0.66, 95% CI: -1.19 to -0.14) or light physical activity (β = -0.40, 95% CI: -0.57 to -0.22) was linked to smaller waist circumferences. Substituting sleep with MVPA was associated with lower BMI (β = -0.31, 95% CI -0.46 to -0.15) and waist circumference (β = -1.46, 95% CI -2.37 to -0.55). Conversely, replacing MVPA with sleep (β = 0.32, 95% CI: 0.27 to 0.37) was associated with higher BMI. Furthermore, greater adherence to the 24HMB guidelines (the number of meeting behavioral recommendations of 24HMB guidelines) was associated with lower risks of obesity, hypertension and diabetes. Conclusion This study demonstrated that the associations between 24HMB reallocations and cardiometabolic health were direction-specific. The most consistent benefits were observed when time was reallocated from sedentary behavior to MVPA, which was associated with lower BMI, smaller waist circumference, and better blood lipids. Trial registration This study has been registered in PROPERO (CRD42024565071).