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

Abstract

lands. Attenuated gastric distress but no benefit to performance with adaptation to octanoate-rich esterified oils in well-trained male cyclists. J Appl Physiol 101: [1733][1734][1735][1736][1737][1738][1739][1740][1741][1742][1743] 2006. First published July 13, 2006; doi:10.1152/japplphysiol.00393.2006.-We investigated the effects of modifying a normal dietary fatty acid composition and ingestion of high-fat exercise supplements on gastrointestinal distress, substrate oxidation, and endurance cycling performance. Nine welltrained male cyclists completed a randomized triple-crossover comprising a 2-wk diet high in octanoate-rich esterified oil (MCFA) or twice long-chain fatty acids (LCFA). Following the diets, participants performed 3-h of cycling at 50% of peak power followed by 10 maximal sprints while ingesting either 1) a carbohydrate (CHO)ϩMCFA-rich oil emulsion after the 2-wk MCFA-rich dietary condition (MC-MC, Intervention) and 2) after one of the LCFA-rich dietary conditions (LC-MC, Placebo) or 3) CHO only following a LCFA-rich diet (LC-CHO, Control). During the 3-h ride MCFAadaptation decreased octanoic-acid oxidation by 24% (90% confidence interval: 14 -34%). The CHOϩMCFA-rich oil emulsion reduced endogenous fat oxidation by 61% (33-89%) and 110% (89 -131%) in the MC-MC and LC-MC conditions, respectively, and MCFA-adaptation reduced endogenous-carbohydrate oxidation by 10% (Ϫ3-23%). MCFA-adaptation attenuated gastrointestinal distress and nausea during the sprints, but the effect of the oil emulsion was to lower sprint power by 10.9% (7.7-14.1%) in the LC-MC condition and by 7.1% (5.7-8.5%) in the MC-MC condition, relative to the LC-CHO control; every one unit increase in nausea decreased mean power by 6.0 W (3.2-8.8 W). We conclude that despite some attenuation of endogenous-carbohydrate oxidation and gastric distress following adaptation to a MCFA-rich diet, repeat sprint performance was substantially impaired in response to the ingestion of a CHOϩMCFA-rich oil emulsion. medium-chain fatty acids; structured triacylglycerols; dietary adaptation; supplementation THE FINITE AVAILABILITY of endogenous glycogen as an energy substrate contributes to the development of fatigue and is therefore a limiting factor in athletic performance during prolonged strenuous exercise (23). 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). Unlike long-chain fatty acids, medium-chain fatty acids (MCFA) can be absorbed more rapidly and directly from the intestinal lumen (5, 13), and their entry into mitochondria does not appear to be rate limited by the acyl-carnitine transfer system to the extent of long chain fatty acids during high-intensity exercise ...

No attenuation of gastric distress or benefit to performance with adaptation to octanoate‐rich esterified oils in female cyclists

“…Meanwhile, the finding of an attenuated response to the intervention relative to the male cohort studied previously (Thorburn, Vistisen et al 2006) is consistent with the generalization that trained females respond with lower amplitude to nutritional-exercise unpublished), carbohydrate loading, and creatine supplementation .…”

“…In male subjects, we (Thorburn, Vistisen et al 2006) previously observed a clear substantial reduction in gastrointestinal distress parameters with MCFA adaptation; and in the covariate analysis, nausea had a moderate-strong reducing effect on sprint mean power. Conversely, in the current cohort of female subjects MCFA adaptation did not clearly attenuate gastrointestinal distress symptoms, and performance was not adversely affected by the intervention relative to the smallest worthwhile detriment in mean power (Table 1), or in relation to the distress marker nausea (Figure 3).…”

“…(Batterham and Hopkins 2006). The smallest substantive change in sprint power was 1.1% as previously (Thorburn, Vistisen et al 2006), with females assumed to be similar (Paton and Hopkins 2005). The smallest standardized (Cohen) change (i.e.…”

“…The within-cyclist standard deviation was estimated from the residual variance. A mechanisms analysis of the relationship between power output and nausea was conducted as described previously (Thorburn, Vistisen et al 2006). …”

“…Though gastric distress was alleviated in these studies, no performance benefit was observed when ingesting MCFA supplements during exercise. We recently investigated whether combining a dietary adaptation period (2-weeks) plus ingestion of a structured triacylglycerol (randomizedstructured MCFA oil+CHO) emulsion during exercise would further attenuate gastric distress, and thereby allow a performance benefit to show through due to greater exogenous-energy supply (Thorburn, Vistisen et al 2006). Gastric distress in response to the MCFA-rich exercise supplement was attenuated during the performance test following the 2-week MCFA adaptation period.…”