Energy replacement diminishes the effect of exercise on postprandial lipemia in boys.

Purpose: Acute bouts of exercise reduce postprandial triacylglycerol concentrations ([TAG]) in healthy boys and girls; however, it is not known whether this effect is mediated by the energy deficit. This study examined whether the exercise-induced reduction in postprandial [TAG] persists after immediate dietary replacement of the exercise energy expenditure (EE).

Methods: Eighteen healthy 11- to 13-year-old boys (mean (SD): body mass 41.3 (8.4)kg; peak oxygen uptake (V̇O2) 55 (5)mL·kg(-1)·min(-1)) completed three, 2-day conditions in a within-measures, crossover design separated by 14days. On day 1, participants rested (CON), exercised at 60% peak V̇O2 inducing a net EE of 32kJ·kg(-1) body mass (EX-DEF) or completed the same exercise with the net EE replaced immediately (EX-REP). On day 2, capillary blood samples were taken in the fasted state and at pre-determined intervals throughout the 6.5h postprandial period. A standardised breakfast and lunch meal were consumed immediately and 4h, respectively, after the fasting sample.

Results: Based on ratios of the geometric means (95% confidence intervals (CI) for ratios), EX-DEF fasting [TAG] was 19% and 15% lower than CON (-32 to -4%, ES=1.15, P=0.02) and EX-REP (-29 to 0%, ES=0.91, P=0.05) respectively; CON and EX-REP were similar (-4%; P=0.59). The EX-DEF total area under the [TAG] versus time curve was 15% and 16% lower than CON (-27 to 0%, ES=0.55, P=0.05) and EX-REP (-29 to -2%, ES=0.62, P=0.03) respectively; CON and EX-REP were not different (2%; -13 to 20%, P=0.80).

Conclusion: Immediate replacement of the exercise-induced energy deficit negates the reduction in postprandial [TAG] in boys; this highlights the importance of maintaining a negative energy balance immediately post-exercise to maximise the metabolic health benefits of exercise.