Is a High Fat Diet the Best for Endurance Athletes?

For the past few years there has been buzz about athletes who follow a high fat diet. Much of their success evidence was anecdotal – until now.

Dr. Jeff Volek, a professor in the Department of Human Sciences at Ohio State University and a Registered Dietitian, is currently wrapping up his study on the correlation of a high fat diet and athletic performance. He has released some information from his study that compares two sets of evenly matched elite male distance runners.

The first set of 10 runners followed a traditional high carbohydrate diet where 60 percent of calories came from carbohydrates, 25 percent from fat and 15 percent from protein. The second set of runners followed a low carbohydrate diet where a mere 10 to 12 percent of calories came from carbohydrates, a whopping 70 percent come from fat and less than 20 percent of the calories came from protein.

More: How to Create Your Ironman Nutrition Plan

Volek has yet to release the complete blood panel and urine analysis, but the results that are currently available are quite interesting.

Fat Oxidation vs. Exercise Intensity

One of the biggest results of Volek's study showed that the fat-adapted athletes burned more fat at a higher pace than the traditional carbohydrate diet group. For endurance athletes, this means they have a significantly lower need for supplemental carbohydrates during training and racing, because more fat is being utilized as fuel.

The high carbohydrate group had maximum fat oxidation at a pace equivalent to around 50 percent of VO2 max. This is the fastest pace the athletes could travel while burning the highest percentage of fat for fuel. Fat oxidation occurred at a rate of roughly 0.5 grams per minute.

The high fat diet group oxidized fat at over 1.2 grams per minute—over double that of the high carbohydrate diet group. Not only was the amount of fat oxidation higher, the high fat diet group was able to travel faster at the high fat fueling rate. This group had maximum fat oxidation at a pace closer to 70 percent of VO2 max.

More: Top 10 Superfoods for Endurance Athletes

Anecdotal evidence outside of this study has reported that fat-adapted, highly-trained ultra-distance runners are completing 100-mile runs in 15 to 25 hours by using only 1,300 to 2,000 supplemental calories during the race. Rough numbers say these athletes are completing 20-hour events on around 100 supplemental calories per hour.

Submaximal run test

Volek also found that during a steady three-hour treadmill run at 65 percent of VO2 max pace, the fat-adapted athletes burned significantly more fat than the high carbohydrate diet athletes.

Numbers released from the study show that if the pace is 65 percent VO2 max, and if the runner consumes the typical high-carbohydrate-diet, roughly 40 percent of the fuel is coming from carbohydrates and 60 percent from fat.

If a high carbohydrate runner is cruising along at a pace that burns 500 calories per hour, he or she is burning around 200 calories per hour of carbohydrates and 300 calories of fat during exercise.

Comparatively, if a fat-adapted runner also burns 500 calories per hour, Volek's study states that he or she will only use 10 percent carbohydrates and 90 percent fat to fuel the run.

The high fat diet runner is burning roughly 50 calories per hour of carbohydrates and 450 calories of fat.

More: Dave Scott's Top 5 Race-day Nutritional Tips

Our high carbohydrate diet runner is burning through carbohydrates at a rate of 200 calories per hour and our fat-adapted diet runner is only burning through 50 carbohydrate calories per hour. This is a huge difference.

Because we store only 1,300 to 2,000 calories of glycogen and fat stores are well in excess of 50,000 calories for most people, Volek's preliminary findings show that utilizing more fat to fuel exercise is beneficial for the endurance athlete.

What we don't know

Athough Volek's study hasn't been entirely released, his conclusions raise a few questions. For example, do fat-adapted women burn more, less or the same amounts of fat during exercise as the men? How does this fueling plan work for athletes that need to sprint or put out intermittent bouts of high effort like road racers, mountain bikers and draft-legal triathletes?

Stay tuned as we learn more about the shifting paradigms of optimal athletic nutrition. Based on this research, you could soon be eating differently to fuel your body.

About the Author

Gale Bernhardt

Gale Bernhardt was the USA Triathlon team coach at the 2003 Pan American Games and 2004 Athens Olympics. She's worked as one of the few World Cup coaches and delivered coached education training for the Triathlon Union's Sport Development Team. She has coached Olympic road racers, World Cup mountain bike riders and Leadville 100 racers. Thousands of athletes have had successful training and racing experiences using Gale's ready-to-use, easy-to-follow training plans.

Gale Bernhardt was the USA Triathlon team coach at the 2003 Pan American Games and 2004 Athens Olympics. She's worked as one of the few World Cup coaches and delivered coached education training for the Triathlon Union's Sport Development Team. She has coached Olympic road racers, World Cup mountain bike riders and Leadville 100 racers. Thousands of athletes have had successful training and racing experiences using Gale's ready-to-use, easy-to-follow training plans.

Discuss This Article