Journal
JOURNAL OF APPLIED PHYSIOLOGY
Volume 111, Issue 1, Pages 108-116Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/japplphysiol.01459.2010
Keywords
skeletal muscle; fasted exercise; fat-rich feeding; energy substrate metabolism; muscle lipids
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Funding
- Katholieke Universiteit Leuven (K.U. Leuven) [OT/05/53]
- Fund for Scientific Research-Flanders, Belgium (F.W.O.-Vlaanderen) [G.0233.05]
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Van Proeyen K, Szlufcik K, Nielens H, Deldicque L, Van Dyck R, Ramaekers M, Hespel P. High-fat diet overrules the effects of training on fiber-specific intramyocellular lipid utilization during exercise. J Appl Physiol 111: 108-116, 2011. First published May 5, 2011; doi:10.1152/japplphysiol.01459.2010.-In this study, we compared the effects of endurance training in the fasted state (F) vs. the fed state [ample carbohydrate intake (CHO)] on exercise-induced intramyocellular lipid (IMCL) and glycogen utilization during a 6-wk period of a hypercaloric (similar to+30% kcal/day) fat-rich diet (HFD; 50% of kcal). Healthy male volunteers (18-25 yrs) received a HFD in conjunction with endurance training (four times, 60-90 min/wk) either in F (n = 10) or with CHO before and during exercise sessions (n = 10). The control group (n = 7) received a HFD without training and increased body weight by similar to 3 kg (P < 0.001). Before and after a HFD, the subjects performed a 2-h constant-load bicycle exercise test in F at similar to 70% maximal oxygen uptake rate. A HFD, both in the absence (F) or presence (CHO) of training, elevated basal IMCL content by similar to 50% in type I and by similar to 75% in type IIa fibers (P < 0.05). Independent of training in F or CHO, a HFD, as such, stimulated exercise-induced net IMCL breakdown by approximately twofold in type I and by approximately fourfold in type IIa fibers. Furthermore, exercise-induced net muscle glycogen breakdown was not significantly affected by a HFD. It is concluded that a HFD stimulates net IMCL degradation by increasing basal IMCL content during exercise in type I and especially IIa fibers. Furthermore, a hypercaloric HFD provides adequate amounts of carbohydrates to maintain high muscle glycogen content during training and does not impair exercise-induced muscle glycogen breakdown.
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