Prolonged sitting negatively affects the postprandial plasma triglyceride-lowering effect of acute exercise

The interaction of prolonged sitting with physical exercise for maintaining health is unclear. We tested the hypothesis that prolonged siting would have a deleterious effect on postprandial plasma lipemia (PPL, postprandial plasma triglycerides) and reduce the ability of an acute exercise bout to attenuate PPL. Seven healthy young men performed three, 5-day interventions [days 1-5 (D1-D5)] in a randomized crossover design with >1 wk between interventions: 1) sitting > 14 h/day with hypercaloric energy balance (SH), 2) sitting >14 h/day with net energy balance (SB), and 3) active walking/standing with net energy balance (WB) and sitting 8.4 h/day. The first high-fat tolerance test (HFTT1) was performed on D3 following 2 days of respective interventions. On the evening of D4 subjects ran on a treadmill for 1 h at ~67% V̇o_2max, followed by the second HFTT (HFTT2) on D5. Two days of prolonged sitting increased TG AUC_I (i.e., incremental area under the curve for TG), irrespective of energy balance, compared with WB (27% in SH, P = 0.003 and 26% in SB, P = 0.046). Surprisingly, after 4 days of prolonged sitting (i.e.; SH and SB), the acute exercise on D4 failed to attenuate TG AUC_I or increase relative fat oxidation in HFTT2, compared with HFTT1, regardless of energy balance. In conclusion, prolonged sitting over 2-4 days was sufficient to amplify PPL, which was not attenuated by acute exercise, regardless of energy balance. This underscores the importance of limiting sitting time even in people who have exercised.