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Authors JW Helge, EA Richter, B Kiens
Title Interaction of Training and Diet on Metabolism and Endurance During
Exercise in Man
Publisher Cambridge Univ Press, 40 West 20TH Street, New York, NY 10011-4211
Abstract 1. Ten untrained young men ingested a carbohydrate-rich diet (65
energy percent (E%) carbohydrate, T-CHO) and ten similar subjects a fat-rich
diet (62 E% fat, T-FAT) while endurance training was performed 3-4 times a
week for 7 weeks. For another 8th week of training both groups ingested the
carbohydrate-rich diet (T-CHO and T-FAT/CHO). 2. Maximal oxygen uptake
increased by 11% (P < 0.05) in both groups after 7 and 8 weeks. Time to
exhaustion at 81% of pre-training maximal oxygen uptake increased
significantly from a mean (+/- S.E.M.) of 35 +/- 4 min to 102 +/- 5 and 65
+/- 7 min in T-CHO and T-FAT, respectively, after 7 weeks (P < 0.05, T-CHO
vs. T-FAT). After 8 weeks, endurance remained unchanged in T-CHO but
increased (P < 0.05) to 77 +/- 9 min in T-FAT/CHO which, however, was still
less (P < 0.05) than in T-CHO. 3. Muscle glycogen breakdown rate during
exercise was halved by endurance training equally in both T-CHO and T-FAT
after 7 and 8 weeks, and muscle glycogen stores at exhaustion were not
depleted in any group. 4. During exercise after 7 weeks, the respiratory
exchange ratio (RER) was unchanged in T-CHO (0.88 +/- 0.01) compared with
pre-training but decreased (P < 0.05) to 0.82 +/- 0.02 in T-FAT. After 8
weeks, RER in both T-CHO and T-FAT/CHO was approximately 0.87. 5. During
exercise, plasma noradrenaline concentration and heart rate were higher in
T-FAT than in T-CHO both at 7 and at 8 weeks. 6. It is concluded that
ingesting a fat-rich diet during an endurance training programme is
detrimental to improvement in endurance. This is not due to a simple lack of
carbohydrate fuel, but rather to suboptimal adaptations that are not remedied
by short-term increased carbohydrate availability. Furthermore, the study
suggests that the decrease in RER usually seen after training when exercising
at the same absolute intensity as before training can be prevented by a
carbohydrate-rich diet.