Discrete Features of Sedentary Behavior Impact Cardiometabolic Risk Factors

Purpose: Sedentary behavior is linked to numerous poor health outcomes. This study aims to determine the effects of 7 d of increased sitting on markers of cardiometabolic risk among free-living individuals. Methods: Ten recreationally active participants (9150 min of moderate-intensity physical activity per week; mean +/- SD age, 25.2 +/- 5.7 yr; mean +/- SD body mass index, 24.9 +/- 4.3 kg.m(-2)) completed a 7-d baseline period and a 7-d sedentary condition in their free-living environment. At baseline, participants maintained normal activity. After baseline, participants completed a 7-d sedentary condition. Participants were instructed to sit as much as possible, to limit standing and walking, and to refrain from structured exercise and leisure time physical activity. ActivPAL (TM) monitor was used to assess sedentary behavior and physical activity. Fasting lipids, glucose, and insulin were measured, and oral glucose tolerance test was performed after baseline and sedentary condition. Results: In comparison to baseline, total sedentary time (mean Delta, 14.9%; 95% CI, 10.2-19.6) and time in prolonged/uninterrupted sedentary bouts significantly increased, whereas the rate of breaks from sedentary time was significantly reduced (mean Delta, 21.4%; 95% CI, 6.9-35.9). For oral glucose tolerance test, 2-h plasma insulin (mean Delta, 38.8 KU.mL(-1); 95% CI, 10.9-66.8) and area under the insulin curve (mean Delta, 3074.1 KU.mL(-1) per 120 min; 95% CI, 526.0-5622.3) were significantly elevated after the sedentary condition. Lipid concentrations did not change. Change in 2-h insulin was negatively associated with change in light-intensity activity (r = -0.62) and positively associated with change in time in sitting bouts longer than 30 min (r = 0.82) and 60 min (r = 0.83). Conclusion: Increased free-living sitting negatively impacts markers of cardiometabolic health, and specific features of sedentary behavior (e.g., time in prolonged sitting bouts) may be particularly important.