Metabolic and performance responses during endurance exercise after high-fat and high-carbohydrate meals

Abstract

We studied the effects of preexercise meal composition on metabolic and performance-related variables during endurance exercise. Eight well-trained cyclists (maximal oxygen uptake 65.0 to 83.5 ml . kg-1 . min-1) were studied on three occasions after an overnight fast. They were given isoenergetic meals containing carbohydrate (CHO), protein (P), and fat (F) in the following amounts (g/70 kg body wt): high-carbohydrate meal, 215 CHO, 26 P, 3 F; high-fat meal, 50 CHO, 14 P, 80 F. On the third occasion subjects were studied after an overnight fast. Four hours after consumption of the meal, subjects started exercise for 90 min at 70% of their maximal oxygen uptake, followed by a 10-km time trial. The high-carbohydrate meal compared with the high-fat meal resulted in significant decreases (P < 0.05) in blood glucose, plasma nonesterified fatty acids, plasma glycerol, plasma chylomicron-triacylglycerol, and plasma 3-hydroxybutyrate concentrations during exercise. This was accompanied by an increase in plasma insulin (P < 0.01 vs. no meal), plasma epinephrine, and plasma growth hormone concentrations (each P < 0.05 vs. either of the other conditions) during exercise. Despite these large differences in substrate and hormone concentrations in plasma, substrate oxidation during the 90-min exercise period was similar in the three trials, and there were no differences in performance on the time trial. These results suggest that, although the availability of fatty acids and other substrates in plasma can be markedly altered by dietary means, the pattern of substrate oxidation during endurance exercise is remarkably resistant to alteration.

Effect of Fat and CHO Meals on Intermittent Exercise in Soccer Players

“…Montain et al [ 19 ] showed that despite similar postprandial insulin concentrations 4 h prior to exercise compared to 12 h postprandially there was a diff erence in CHO oxidation and fat metabolites between conditions, supporting a long lasting eff ect of insulin. Consistent with the current investigation Whitley et al [ 28 ] reported no significant diff erences in insulin concentrations following the consumption of either a HFM or HCM during exercise. However, again insulin was not analysed postprandially so similar caveats to the present investigations may be warranted.…”

“…These fi ndings suggest that the type of meal ingested prior to soccer simulated exercise has an impact on metabolism, but not on the subsequent performance as determined in the present study. no improvements in performance for a cycling capacity test [ 21 , 22 ] or for time trial performance [ 28 ] , critically these studies demonstrate no performance decrements. Underlying these observations is the principle that a HFM enables an increase in fatty acids (FA) availability during the postprandial period and onset of exercise, an increase in the rate of fat oxidation resulting in a matched or enhanced performance.…”

“…The observations of FA are consistent with others who report increases over the 90 min of match play, irrespective of the preexercise nutritional strategies employed [ 15 ] . Meals that are high in CHO suppress plasma FA concentrations [ 28 ] , which may be the case since the HFM contained 59.4 g of CHO compared to 160 g with the HCM. Elevated glycerol concentrations following the HFM were observed in the current study and are in agreement with others [ 28 ] .…”

“…Meals that are high in CHO suppress plasma FA concentrations [ 28 ] , which may be the case since the HFM contained 59.4 g of CHO compared to 160 g with the HCM. Elevated glycerol concentrations following the HFM were observed in the current study and are in agreement with others [ 28 ] . This fi nding may be indicative of an enhanced rate of lipolysis.…”

Attenuated gastric distress but no benefit to performance with adaptation to octanoate-rich esterified oils in well-trained male cyclists

“…An increase in plasma free fatty acid (FFA) and fat oxidation has been shown to spare endogenous glycogen, most reliably via fat infusion studies (38). However, fat infusion during racing conditions is not feasible, and long-chain triglyceride ingestion before or during exercise has not been shown to enhance performance (14,32,40). More recently, interest has focused on the ingestion of medium-chain triglycerides (MCTs).…”