Effect of endogenous carbohydrate availability on oral medium-chain triglyceride oxidation during prolonged exercise

Mar 1, 1996Journal of applied physiology (Bethesda, Md. : 1985)

How natural carbohydrate levels affect the use of medium-chain fats during long exercise

AI simplified

Circadian Biology on OpenScience ↗PubMed ↗DOI ↗

Abstract

85% of ingested medium-chain triglycerides (MCT) were oxidized after a low-glycogen trial.

MCT oxidation was measured during a 60- to 90-minute exercise period.
There was no significant difference in MCT utilization between low-glycogen and normal-to-high glycogen states.
Peak MCT oxidation rates were 0.15 g/min for low glycogen and 0.13 g/min for normal-to-high glycogen.
MCT contributed 7.6% to total energy expenditure in the low-glycogen state and 6.5% in the normal-to-high glycogen state.
Total fatty acid oxidation was significantly higher in the low-glycogen trial, but MCT ingestion did not influence this effect.
Carbohydrate oxidation decreased in the low-glycogen condition, with no observable impact from MCT.

AI simplified

The present study examined the medium-chain triglyceride (MCT) oxidation rate of oral carbohydrate (CHO) + MCT supplements after a glycogen-depletion trial [low glycogen (LG)] and in the glycogen-loaded state [normal-to-high glycogen (HG)]. Eight elite athletes cycled four times 90 min at 50% maximal workload (57% maximal O2 uptake). In two trials, they followed a LG protocol to achieve low-glycogen stores in the leg muscles the evening before the experiment, and in two trials they followed a HG protocol. Subjects received a bolus of 4 ml/kg at the start and 2 ml/kg every 20 min during exercise of either a 15% CHO (long-chain glucose polymer) solution or an equicaloric CHO + MCT suspension. Exogenous MCT oxidation was measured by adding a [1,1,1-13C]trioctanoate tracer to the MCT oil and measuring 13CO2 production in the breath. The results show that 85% of MCT ingested was oxidized in LG and 69% in HG during the 60- to 90-min period. There was no statistically significant difference in MCT utilization between LG and HG. Peak oxidation rates were 0.15 and 0.13 g/min, respectively. MCT contributed 7.6% (LG) and 6.5% (HG) to total energy expenditure during the 60- to 90-min period. Total fatty acid oxidation was significantly elevated in the LG trial but was not influenced by MCT ingestion. Concomitantly, CHO oxidation was reduced in LG but no effect of MCT was observed. We conclude that 1) the contribution of MCT to total energy expenditure was small and 2) strenuous exercise the day before the experiment, followed by a low CHO intake and leading to a low CHO availability, substantially increased total fat oxidation but did not significantly increase MCT oxidation.

Full Text

Full text is available at the source.

View full text ↗

Effect of endogenous carbohydrate availability on oral medium-chain triglyceride oxidation during prolonged exercise

Abstract

Full Text

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief

Abstract

Full Text

Related papers

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief