Mice that are used to exercising can still run just as far on very low-carb diets as they do on higher-carb ones — their muscles might be adapting to save energy and switch fuels efficiently.

What we've found so far suggests that low-carbohydrate diets do not reduce endurance in trained mice. The evidence we've reviewed leans toward the idea that these animals can maintain their running capacity even when consuming very few carbohydrates [1]. We analyzed the available research and found 14.0 supporting assertions and no studies that refute this effect. Specifically, one key finding shows that mice accustomed to exercise are able to run just as far on very low-carb diets as they are on higher-carb ones [1]. This suggests their bodies may be adapting in ways that help preserve energy and efficiently switch between fuel sources, likely by increasing fat utilization during physical activity. Our current analysis does not indicate a decline in endurance performance due to low carbohydrate intake in this group of animals. However, all the evidence we’ve reviewed comes from studies on mice that are already trained for physical activity, so we cannot say whether the same would hold true for untrained mice or other species, including humans. We also don’t have data on how long these effects last or what might happen under more intense exercise conditions. Since we’ve only reviewed a limited number of assertions so far, our understanding is still developing. The takeaway: in trained mice, cutting carbs very low doesn’t seem to hurt their endurance based on what we’ve seen. Their muscles may adapt to use fuel more efficiently. But we’re still gathering evidence — this is just one piece of a larger picture.