Abstract
Background/Objectives:Exercise performed shortly before (that is, within half a day of) a high-fat meal is beneficial for stimulating fat oxidation after the meal and reducing postprandial triglycerides (TG). This benefit of exercise is unfortunately negated if the after-exercise food choice to replace the calories expended during exercise is one containing high-glycemic index (HGI) carbohydrates. We determined the effect of consuming low-glycemic index (LGI) carbohydrates after an exercise session on fat oxidation and TG after a subsequent high-fat meal.Subjects/Methods:Using a randomized, counterbalanced crossover design, 23 overweight or obese individuals (body mass index ⩾25 kg m−2) performed: walking exercise (90 min) at 1800 h followed by no meal (EX); exercise followed by a meal with LGI carbohydrates (that is, lentils, EX-LGI); exercise followed by a meal with HGI carbohydrates (that is, instant potatoes, white bread, EX-HGI); and a control condition with no exercise or meal. After a 10-h overnight fast, participants were given a standardized high-fat meal. Fat oxidation was estimated before and for 6 h after this meal from respiratory gas measures and TG determined from blood samples.Results:Fat oxidation (mean±s.d.) was higher with EX (6.9±1.7 g h−1) than EX-HGI (6.3±1.6 g h−1; P=0.007) and Control (5.9±1.7 g h−1; P=0.00002), and EX-LGI (6.6±1.7 g h−1) was higher than Control (P=0.002). TG total area under the curve was 18–32% lower with EX and EX-LGI compared with control (P=0.0005 and P=0.0001, respectively) and EX-HGI (P=0.05 and P=0.021, respectively).Conclusions:A meal containing HGI carbohydrates consumed after an evening exercise session cancels the beneficial effect of exercise for stimulating fat oxidation and lowering TG after a subsequent high-fat meal, whereas consuming a post-exercise meal with LGI carbohydrates retains the positive effect of exercise.
Highlights
Respiratory exchange ratio was lower for exercise followed by a low GI (LGI) meal (EX-LGI) (0.74 ± 0.01), exercise without caloric replacement (EX) (0.74 ± 0.01) and exercise followed by a high-glycemic index (HGI) meal (EX-HGI) (0.76 ± 0.01) compared with control (0.77 ± 0.01) (Po0.01), and for EX-LGI and EX compared with EX-HGI (Po0.01)
Fat oxidation was significantly higher in the EX condition (6.9 ± 1.7 g h− 1) than EX-HGI
Insulin inhibits fat oxidation,[13] and the lower insulin level in the EX-LGI condition could have allowed superior fat oxidation and greater clearance of TG compared with the EX-HGI condition
Summary
Postprandial lipids, the level of triglycerides (TG) after a meal, are associated with arteriosclerotic plaque formation[1] and are a more potent predictor of cardiovascular disease risk than fasting lipids because most of an individual’s day is spent in the postprandial state.[2,3,4] This problem is especially evident in overweight and obese individuals who have an elevated postprandial TG response compared with lean individuals.[5]Exercise performed within 24 h of a high-fat meal increases whole-body fat oxidation and reduces the postprandial elevation of TG in the blood;[6] exercise only has this beneficial effect if it is followed by a period of fasting before the subsequent meal.[7,8] The effect of exercise for increasing fat oxidation and reducing postprandial TG is negated if the post-exercise food consumed to compensate for the caloric deficit elicited by the exercise is in the form of high-glycemic index (HGI) carbohydrates.[7,8] Performing an exercise session and fasting could be considered an unnatural state because one usually consumes food after exercise either to enhance recovery[9] or because exercise increases appetite.[10]. The consumption of low GI (LGI) carbohydrates results in lower and more sustained levels of blood glucose and a smaller release of insulin.[11,12] HGI foods may attenuate the fat oxidation stimulated by exercise because insulin inhibits fat oxidation.[13] Meals with LGI that elicit a lower insulin release have the potential to better preserve the effects of exercise for attenuating postprandial triglycerides after a subsequent meal; the use of LGI meals in the recovery period after exercise has never been evaluated for affecting next-day postprandial TG levels. It was hypothesized that compared with consuming a HGI meal post exercise, a LGI meal would elicit a lower insulin response the day, enhance fat oxidation and attenuate the increase in TG after a high-fat breakfast
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
