Postprandial triacylglycerol in adolescent boys: A case for moderate exercise

Purpose: To compare the effects of 60-min bouts of intermittent moderate and vigorous exercise on postprandial plasma triacylglycerol (TAG) metabolism in eight healthy adolescent boys (mean +/- SD age: 13 +/- 0.3 yr). Methods: Participants completed three conditions in a counterbalanced order. On day 1, they either rested for 110 min (CON), completed 6 x 10-min blocks of intermittent treadmill exercise at 53% peak VO2 (MOD), or 6 x 10-min blocks at 75% peak VO2 (VIG). On day 2 after a 12-h fast, a capillary blood sample was taken for [TAG] and [glucose] (mmol.L-1) and then a high-fat milkshake was consumed (1.50 g.kg(-1) fat, 1.22 g.kg(-1) CHO, and 0.22 g.kg(-1) protein; 80 kJ.kg(-1)). Further blood samples were taken every hour for a 6-h postprandial rest period for [TAG] and [glucose]. Results: Estimated energy expenditure was 45% higher in VIG than in MOD (95% confidence interval [CI] 23-72%). Fasting [TAG] and [glucose] did not differ between the conditions. Average [TAG] for the postprandial period was lower by 24% in MOD (95% CI -47% to 9%, P = 0.06) and by 21% in VIG (95% CI -42% to 8%, P = 0.08) than CON, with no meaningful difference (4%; 95% CI -27% to 48%, P = 0.50) between MOD and VIG. The total area under the [TAG] versus time curve (mmol.L-1 6 h) was lower by 24% in MOD (95% CI -42% to 0%, P = 0.05) and by 20% in VIG (95% CI -37% to 0%, P = 0.07) than CON. MOD and VIG were not different from each other (4%; 95% CI -18% to 32%, P = 0.54). Conclusion: Both 60 min of moderate and vigorous intermittent exercises reduced postprandial [TAG]. However, the extra energy expended in the vigorous condition did not produce a dose-related reduction compared with the moderate-intensity condition.