Exercise energy expenditure and postprandial lipemia in girls

Purpose
This study aimed to examine the effect of 30 and 60 min of moderate-intensity treadmill walking on postprandial triacylglycerol concentrations ([TAG]) in healthy girls.

Methods
Eighteen 10- to 14-yr-old girls (mean ± SD; body mass = 48 ± 11 kg, body fat = 19.0 ± 4.6%, peak oxygen uptake [V˙O2] = 47 ± 6 mL·kg−1·min−1) completed three 2-d trials in a counterbalanced crossover design, each separated by 14 d. On day 1, they rested (CON) or completed 30 min (EX30) or 60 min (EX60) of intermittent treadmill exercise at 56% peak V˙O2, inducing energy expenditures of 777 and 1536 kJ (186 and 367 kcal), respectively. On day 2, after a 12-h fast, a capillary blood sample was taken for fasting [TAG] before a high-fat milkshake (80 kJ·kg−1 body mass) was consumed. Further blood samples were taken hourly over a 6-h postprandial rest period for [TAG]. ANOVA and Student’s t-tests were used to analyze the data.

Results
Fasting [TAG] was lower in EX60 than CON (95% confidence interval [CI] = –0.36 to 0.04, effect size (ES) = 0.41) and EX30 (95% CI = –0.47 to 0.04, ES = 0.46); all group mean concentrations were low (≤0.90 mmol·L−1). The main effect for condition revealed differences in postprandial [TAG] over time (ES = 0.36). The EX60 total area under the [TAG] versus time curve was lower than CON (95% CI = –2.66 to –0.04, ES 0.40) and EX30 (95% CI = –2.11 to 0.15, ES = 0.30); CON and EX30 were similar (95% CI = –1.44 to 0.71, ES = 0.10).

Conclusion
This study demonstrates that 60 min but not 30 min of moderate treadmill exercise, with a gross energy expenditure of 1536 kJ (367 kcal), attenuated postprandial [TAG] in girls.