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Maximal Fat Oxidation In High-level Ultra-marathon Runners Habitually Consuming Very Low-carbohydrate And High-carbohydrate Diets

1799 Board #144 May 28, 2

00 PM - 3

30 PM

Davitt, Patrick M.; Saenz, Catherine; Freidenreich, Daniel J.; Kunces, Laura J.; Apicella, Jenna M.; Creighton, Brent C.; Aerni, Giselle A.; Anderson, Jeffrey M.; Maresh, Carl M. FACSM; Kraemer, William J. FACSM; Volek, Jeff S.

Medicine & Science in Sports & Exercise: May 2015 - Volume 47 - Issue 5S - p 488
doi: 10.1249/
D-32 Free Communication/Poster - Fat Metabolism I Thursday, May 28, 2015, 1: 00 PM - 6: 00 PM Room: Exhibit Hall F

1Mercy College, Dobbs Ferry, NY. 2The Ohio State University, Columbus, OH. 3Central Connecticut State University, New Britain, CT. 4University of Connecticut, Storrs, CT.


(No relationships reported)

Previous research has indicated that maximal rates of fat oxidation (FATox) are less than 1 g/min, but this has not been tested in high-level athletes habitually following a diet restricted in carbohydrates. A growing number of elite ultra-endurance athletes have switched to a high-fat, low-carbohydrate diet to maximize FATox and enhance performance.

PURPOSE: To examine maximal fat oxidation rates and the intensity at which such fat oxidation occurs (i.e., %VO2max), between high-level ultra-marathoners consuming either low-carbohydrate/high-fat (LCD) or high-carbohydrate/low-fat diets (HCD).

METHODS: 20 elite level ultra-running men (age 33.5 ± 6.4 yr, weight 67.1 ± 7.7 kg, BMI 22.6 ± 3.3 kg/m2) habitually consuming a HCD (n=10; 58% CHO, 15% PRO, 28% FAT) or LCD (n=10; 11% CHO, 19% PRO, 71% FAT) for at least 6 months were matched for age and competition performance. They performed a maximal capacity graded exercise test on a high-speed treadmill to measure maximal aerobic capacity (VO2max). Stages were two minutes in duration and continual indirect calorimetry was analyzed via a TrueOne 2400 metabolic cart, fitted with a Hans Rudolph 7450 V2 facemask. Participants ran until volitional fatigue.

RESULTS: There were no significant differences in VO2max between groups (HCD 64.3 ± 6.2; LCD 64.7 ± 3.7 mL/kg/min) (P = 0.850). There was a significant difference in maximal FATox (HCD 0.67 g/min; LCD 1.54 g/min) (P<0.0001) and %VO2max @ maximal FATox (HCD 54.89%; LCD 70.25%) (P<0.0001). There was a significant difference in maximal CHOox (HCD 7.83 g/min; LCD 5.65 g/min) (P = 0.002).

CONCLUSION: Adaptation to a LCD in elite ultrarunners results in profound increases in maximal fat oxidation at least 50% greater than the highest rates ever reported. These findings underscore the robust effect very low-carbohydrate diets have on accelerating fat oxidation beyond that achieved with chronic training in high-level athletes.

© 2015 American College of Sports Medicine