title: Metabolic characteristics of keto-adapted ultra-endurance runners.
abstract: BACKGROUND
  Many successful ultra-endurance athletes have switched from a high-carbohydrate to a low-carbohydrate diet, but they have not previously been studied to determine the extent of metabolic adaptations.
  
  
  METHODS
  Twenty elite ultra-marathoners and ironman distance triathletes performed a maximal graded exercise test and a 180 min submaximal run at 64% VO2max on a treadmill to determine metabolic responses. One group habitually consumed a traditional high-carbohydrate (HC: n=10, %carbohydrate:protein:fat=59:14:25) diet, and the other a low-carbohydrate (LC; n=10, 10:19:70) diet for an average of 20 months (range 9 to 36 months).
  
  
  RESULTS
  Peak fat oxidation was 2.3-fold higher in the LC group (1.54±0.18 vs 0.67±0.14 g/min; P=0.000) and it occurred at a higher percentage of VO2max (70.3±6.3 vs 54.9±7.8%; P=0.000). Mean fat oxidation during submaximal exercise was 59% higher in the LC group (1.21±0.02 vs 0.76±0.11 g/min; P=0.000) corresponding to a greater relative contribution of fat (88±2 vs 56±8%; P=0.000). Despite these marked differences in fuel use between LC and HC athletes, there were no significant differences in resting muscle glycogen and the level of depletion after 180 min of running (-64% from pre-exercise) and 120 min of recovery (-36% from pre-exercise).
  
  
  CONCLUSIONS
  Compared to highly trained ultra-endurance athletes consuming an HC diet, long-term keto-adaptation results in extraordinarily high rates of fat oxidation, whereas muscle glycogen utilization and repletion patterns during and after a 3 hour run are similar.
authors.affiliation: Department of Kinesiology, University of Connecticut, Storrs, CT, USA; Department of Human Sciences, The Ohio State University, Columbus, OH, USA. Electronic address: volek.1@osu.edu.
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Volek
authors.affiliation: Department of Kinesiology, University of Connecticut, Storrs, CT, USA; Department of Human Sciences, The Ohio State University, Columbus, OH, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Freidenreich
authors.affiliation: Department of Kinesiology, University of Connecticut, Storrs, CT, USA; Department of Human Sciences, The Ohio State University, Columbus, OH, USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: Saenz
authors.affiliation: Department of Kinesiology, University of Connecticut, Storrs, CT, USA.
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Kunces
authors.affiliation: Department of Kinesiology, University of Connecticut, Storrs, CT, USA.
authors.forename: Brent C
authors.initials: BC
authors.lastname: Creighton
authors.affiliation: Department of Kinesiology, University of Connecticut, Storrs, CT, USA.
authors.forename: Jenna M
authors.initials: JM
authors.lastname: Bartley
authors.affiliation: Department of Kinesiology, University of Connecticut, Storrs, CT, USA.
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Davitt
authors.affiliation: Department of Kinesiology, University of Connecticut, Storrs, CT, USA.
authors.forename: Colleen X
authors.initials: CX
authors.lastname: Munoz
authors.affiliation: Department of Kinesiology, University of Connecticut, Storrs, CT, USA.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Anderson
authors.affiliation: Department of Kinesiology, University of Connecticut, Storrs, CT, USA; Department of Human Sciences, The Ohio State University, Columbus, OH, USA.
authors.forename: Carl M
authors.initials: CM
authors.lastname: Maresh
authors.affiliation: Department of Kinesiology, University of Connecticut, Storrs, CT, USA.
authors.forename: Elaine C
authors.initials: EC
authors.lastname: Lee
authors.affiliation: Department of Anatomy, University of New England, Biddeford, ME, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Schuenke
authors.affiliation: Department of Kinesiology, University of Connecticut, Storrs, CT, USA.
authors.forename: Giselle
authors.initials: G
authors.lastname: Aerni
authors.affiliation: Department of Kinesiology, University of Connecticut, Storrs, CT, USA; Department of Human Sciences, The Ohio State University, Columbus, OH, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Kraemer
authors.affiliation: School of Medicine (emeritus), University of California, Davis, Davis, CA, USA.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Phinney
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D015308:Anaerobic Threshold; D003430:Cross-Sectional Studies; D050528:Diet, Carbohydrate-Restricted; D004040:Dietary Carbohydrates / Q000494:pharmacology; D004041:Dietary Fats / Q000378:metabolism; D005080:Exercise Test; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism; D010084:Oxidation-Reduction; D010807:Physical Endurance / Q000502:physiology*; D012420:Running / Q000502:physiology*; D055815:Young Adult
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D006003:Glycogen
keywords: carbohydrate; exercise; fat; glycogen; metabolism