Reduction in postprandial lipemia after walking: influence of exercise intensity

This study compared the effects of low and moderate intensity walking on postprandial lipemia, holding energy expenditure constant. Nine healthy normolipidemic subjects (5 men, 4 women; age 27.7 +/- 0.9, fasting, plasma triacylglycerol 0.95 +/- 0.18 mmol.l-1, mean +/- SEM) who were physically active but not endurance-trained undertook three trials, each over 2 d, in a balanced design. On the afternoon of day 1 they either refrained from exercise (Control), walked for 3 h at low intensity (Walk low, 32 +/- 1% VO2max), or walked for 1.5 h at moderate intensity (Walk moderate, 63 +/- 1% VO2max). The following morning, after a 12-h fast, they consumed a high-fat meal (1.3 g fat, 1.2 g carbohydrate, 0.2 g protein, 76 kJ energy per kg body mass). Blood and expired air samples were obtained before the meal and for 6 h afterward. Postprandial lipemia (total area under triacylglycerol concentration vs time curve) was lower than control after low intensity walking as well as after moderate intensity walking (both P < 0.05) but did not differ between the two walking trials (Control, 8.09 +/- 1.09 mmol.l-1 h; Walk low, 5.46 +/- 0.63 mmol.l-1.h; Walk moderate, 5.53 +/- 0.58 mmol.l-1.h). The increase in energy production following the test meal did not differ between trials, but fat oxidation was increased in the fasting and postprandial states for both walking trials, compared with control (P < 0.05).