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Effect of caffeine co-ingested with carbohydrate or fat on metabolism and performance in endurance-trained men

Published online by Cambridge University Press:  31 July 2001

Talia L. Jacobson ,
Mark A. Febbraio ,
Melissa J. Arkinstall  and
John A. Hawley
Talia L. Jacobson
Affiliation:
Exercise Metabolism Group, Department of Human Biology and Movement Science, RMIT University, Bundoora 3083, Victoria and Exercise Physiology and Metabolism Laboratory, Department of Physiology, The University of Melbourne, Parkville 3052, Melbourne, Australia
Mark A. Febbraio
Affiliation:
Exercise Metabolism Group, Department of Human Biology and Movement Science, RMIT University, Bundoora 3083, Victoria and Exercise Physiology and Metabolism Laboratory, Department of Physiology, The University of Melbourne, Parkville 3052, Melbourne, Australia
Melissa J. Arkinstall
Affiliation:
Exercise Metabolism Group, Department of Human Biology and Movement Science, RMIT University, Bundoora 3083, Victoria and Exercise Physiology and Metabolism Laboratory, Department of Physiology, The University of Melbourne, Parkville 3052, Melbourne, Australia
John A. Hawley
Affiliation:
Exercise Metabolism Group, Department of Human Biology and Movement Science, RMIT University, Bundoora 3083, Victoria and Exercise Physiology and Metabolism Laboratory, Department of Physiology, The University of Melbourne, Parkville 3052, Melbourne, Australia
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Abstract

We examined the effect of caffeine co-ingested with either carbohydrate or fat on metabolism and performance in eight endurance-trained subjects who performed a random order of four experimental trials consisting of 120 min of steady-state ergometer cycling at 70 % of maximal O2 uptake (SS) followed by a time trial in which subjects completed a set amount of work (7 kJ kg-1) as quickly as possible. One hour before SS subjects ingested either 2.6 g kg-1 carbohydrate (CHO); 2.6 g kg-1 CHO + 6 mg kg-1 caffeine (CHO + CAF); 1.2 g kg-1 fat with 2000 U I.V. heparin (FAT); or 1.2 g kg-1 fat with 2000 U I.V. heparin + 6 mg kg-1 caffeine (FAT + CAF). The rate of carbohydrate oxidation was higher (µmol kg-1 min-1: CHO, 243 ± 39 and CHO + CAF, 239 ± 30 vs. FAT, 196 ± 48 and FAT + CAF, 191 ± 55; P < 0.05, values are means ± S.D.) and the rate of fat oxidation lower (µmol kg-1 min-1: CHO, 19 ± 8 and CHO + CAF, 22 ± 7 vs. FAT, 35 ± 19 and FAT + CAF, 37 ± 17; P < 0.05) with carbohydrate than fat ingestion. Yet despite lower carbohydrate use with fat feeding, the time taken to complete the time trial was less after carbohydrate than after fat ingestion (min: CHO, 30.37 ± 7.42 and CHO + CAF, 29.12 ± 5.62 vs. FAT, 33.02 ± 8.50 and FAT + CAF, 32.78 ± 7.70; P < 0.05). We conclude that (1) caffeine co-ingested with either carbohydrate or fat meals has no additive effect on substrate utilization or exercise performance and (2) carbohydrate ingestion before exercise improves subsequent time trial performance compared with fat ingestion. Experimental Physiology (2001) 86.1, 137-144.

Type
Research Article
Information
Experimental Physiology , Volume 86 , Issue 1 , January 2001 , pp. 137 - 144
Copyright
© The Physiological Society 2001

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