title: High-fat diet overrules the effects of training on fiber-specific intramyocellular lipid utilization during exercise.
abstract: 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 (∼+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 ∼3 kg (P < 0.001). Before and after a HFD, the subjects performed a 2-h constant-load bicycle exercise test in F at ∼70% maximal oxygen uptake rate. A HFD, both in the absence (F) or presence (CHO) of training, elevated basal IMCL content by ∼50% in type I and by ∼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.
authors.affiliation: Research Centre for Exercise and Health, Department of Biomedical Kinesiology, Katholieke Universiteit Leuven, Leuven, Belgium.
authors.forename: Karen
authors.initials: K
authors.lastname: Van Proeyen
authors.forename: Karolina
authors.initials: K
authors.lastname: Szlufcik
authors.forename: Henri
authors.initials: H
authors.lastname: Nielens
authors.forename: Louise
authors.initials: L
authors.lastname: Deldicque
authors.forename: Raf
authors.initials: R
authors.lastname: Van Dyck
authors.forename: Monique
authors.initials: M
authors.lastname: Ramaekers
authors.forename: Peter
authors.initials: P
authors.lastname: Hespel
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001530:Belgium; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000378:metabolism; D004041:Dietary Fats / Q000008:administration & dosage / Q000378:metabolism*; D002149:Energy Intake; D004734:Energy Metabolism; D015444:Exercise; D005080:Exercise Test; D005215:Fasting / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood; D015971:Gene Expression Regulation, Enzymologic; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D050356:Lipid Metabolism; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption; D010766:Phosphorylation; D010807:Physical Endurance; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D015430:Weight Gain; D055815:Young Adult
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D005230:Fatty Acids, Nonesterified; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D012333:RNA, Messenger; D006003:Glycogen; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; D000103:Acetyl-CoA Carboxylase