title: Short-term high-fat diet alters substrate utilization during exercise but not glucose tolerance in highly trained athletes.
abstract: We determined the effect of a high-fat diet and carbohydrate (CHO) restoration on substrate oxidation and glucose tolerance in 7 competitive ultra-endurance athletes (peak oxygen uptake [VO(2peak)] 68 +/- 1 ml x kg(-1) x min(-1); mean +/- SEM). For 6 days, subjects consumed a random order of a high-fat (69% fat; FAT-adapt) or a high-CHO (70% CHO; HCHO) diet, each followed by 1 day of a high-CHO diet. Treatments were separated by an 18-day wash out. Substrate oxidation was determined during submaximal cycling (20 min at 65% VO(2peak)) prior to and following the 6 day dietary interventions. Fat oxidation at baseline was not different between treatments (17.4 +/- 2.1 vs. 16.1 +/- 1.3 g x 20 min(-1) for FAT-adapt and HCHO, respectively) but increased 34% after 6 days of FAT-adapt (to 23.3 +/- 0.9 g x 20 min(-1), p < .05) and decreased 30% after HCHO (to 11.3 +/- 1.4 g x 20 min(-1), p < .05). Glucose tolerance, determined by the area under the plasma [glucose] versus time curve during an oral glucose tolerance (OGTT) test, was similar at baseline (545 +/- 21 vs. 520 +/- 28 mmol x L(-1) x 90 min(-1)), after 5-d of dietary intervention (563 +/- 26 vs. 520 +/-18 mmol x L(-1) x 90 min(-1)) and after 1 d of high-CHO (491 +/- 28 vs. 489 +/- 22 mmol x L(-1) x 90 min(-1) for FAT- adapt and HCHO, respectively). An index of whole-body insulin sensitivity ( S(I), 10000/divided by fasting [glucose] x fasting [insulin] x mean [glucose] during OGTT x mean [insulin] during OGTT) was similar at baseline (15 +/- 2 vs. 17 +/- 5 arbitrary units), after 5-d of dietary intervention (15 +/- 2 vs. 15 +/- 2) and after 24 h of CHO loading (17 +/- 3 vs. 18 +/- 2 for FAT- adapt and HCHO, respectively). We conclude that despite marked changes in the pattern of substrate oxidation during submaximal exercise, short-term adaptation to a high-fat diet does not alter whole-body glucose tolerance or an index of insulin sensitivity in highly-trained individuals.
authors.affiliation: Exercise Metabolism Group, School of Medical Sciences, RMIT University, Bundoora, Victoria 3083, Australia.
authors.forename: H M
authors.initials: HM
authors.lastname: Staudacher
authors.forename: A L
authors.initials: AL
authors.lastname: Carey
authors.forename: N K
authors.initials: NK
authors.lastname: Cummings
authors.forename: J A
authors.initials: JA
authors.lastname: Hawley
authors.forename: L M
authors.initials: LM
authors.lastname: Burke
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D004041:Dietary Fats / Q000008:administration & dosage / Q000378:metabolism*; D015444:Exercise; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D004041:Dietary Fats; D007328:Insulin