Effect of Morning Exercise on Daily Post-prandial Triglcerides

Abstract

PURPOSE: An increased post-prandial triglyceride (PPTG) excursion is an independent risk factor for coronary heart disease, therefore, evaluating factors that increase or decrease this parameter is important. Women reportedly have a lower PPTG after a single meal compared to men whereas moderate exercise decreases PPTG after consumption of a single, very high fat meal. The aims of this study, therfore, were to a) determine if a single bout of morning exercise can significantly decrease PPTGs over an entire day, when consuming meals of a more typical macronutrient composition and b) to determine if there is a sex difference in the daily PPTG excursion with and/or without exercise. METHODS: Non-obese (BMI 20-27 kg/m2), untrained, healthy, women (n = 11) and men (n = 12) were recruited and matched for fasting TG levels (101 ± 27 and 100 ± 14 mg/dl, respectively). Subjects completed an exercise and a rest study day (randomized order) separated by 3-4 weeks. Prior to each study day, subjects consumed a controlled diet (5 days) and abstained from planned exercise (60 hrs). After an overnight stay on the clinical research unit, subjects commenced testing at 7:15 am after an overnight fast. On the exercise day, subjects walked on a treadmill for 60 mins at 60% VO2 peak and on the rest day, subjects rested for the same time period. Breakfast was consumed at 8:30 am, with lunch and dinner at 12:30 pm and 5:30 pm, respectively. Macronutrient composition of each meal was 34% fat, 15% protein and 51% carbohydrate. Subjects remained resting from 8:30 am onwards and energy intake was calculated to meet energy requirements of the corresponding day. Blood samples were drawn before exercise (or rest) and continued throughout the remainder of the day (total of 26 time points). RESULTS: The integrated area under the curve (IAUC) for total TGs over the entire day was significantly lower on the exercise vs rest day in both women (7766 ± 2977 vs 22947 ± 2979 mg/dl/840 mins, respectively P < 0.0001) and men (20196 ± 5660 vs 29721 ± 5252 mg/dl/840 mins). There was an overall significant sex difference in the daily PPTG excursion (IAUC, P = 0.05), mainly due to the lower response in women vs men on the exercise day (P = 0.07). In both sexes, the difference in the PPTG excursion on the exercise vs rest day was greatest after lunch (P = 0.0003 women, P = 0.03 men) and dinner (P < 0.0001 and P = 0.05, respectively). There were no sex or day differences in the daily insulin and glucose excursions. CONCLUSIONS: In conclusion, a single bout of moderate exercise can reduce the daily PPTG response when consuming meals of a typical macronutrient composition, and this response tends to be more pronounced in women vs men.