In a recent study, researchers find that elite endurance athletes who eat very few carbohydrates can burn more than twice as much fat as high-carb athletes during maximum exertion and prolonged exercise.
The finding is published in Metabolism. Researchers from Ohio State University led the study. They tested 20 elite ultra-marathoners and ironman distance triathletes.
All participants performed a maximal graded exercise test and a 180 minutes submaximal run on a treadmill. One group ate a traditional high-carbohydrate diet, and the other group ate a low-carbohydrate diet.
The low-carbohydrate diet consisted of 10 percent carbs, 19 percent protein and 70 percent fat. The high-carbohydrate diet consisted of 59 percent carbs, 14 percent protein and 25 percent fat.
Before the test, both groups had eaten their diet for an average of 20 months.
Researchers tested the fat-burning rates in both groups when the athletes were doing treadmill tests.
They found that on average, the low-carb runners’ peak fat-burning rate was 2.3-fold higher than the rate for high-carb athletes: 1.5 versus .67 grams per minute.
In addition, the average contribution of fat during exercise in the low-carb and high-carb groups was 88 percent and 56 percent, respectively.
Researchers suggest that the low-carb athletes go beyond what people can achieve with good genetics and extensive training. It seems that if carbs are restricted in diet, human can burn much more fat.
Another interesting finding is that the low-carb athletes had normal muscle glycogen levels to store carbohydrates.
They also broke down the same level of glycogen as the high-carb runners during the long run, and synthesized the same amount of glycogen in their muscles during recovery as the high-carb athletes.
Researchers suggest that restricting carbs allows the body to boot an alternative metabolic operating system and enable many athletes to achieve improved levels of health and performance.
Citation: Volek JS, et al. (2015). Metabolic characteristics of keto-adapted ultra-endurance runners. Metabolism, 2015. DOI: 10.1016/j.metabol.2015.10.028.
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