Can Carbs Boost Performance on a Keto Diet?
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Many endurance athletes are experimenting with the ketogenic diet (KD), which is very low in carbohydrates and high in fat. The idea is to train the body to use fat as its main fuel, which is helpful in long-distance events. But a new study has found something surprising: eating carbs right before a race might still give these keto athletes a boost.
What Did the Study Look At?
Researchers studied 13 recreational athletes who had been following a strict keto diet for over a year. These athletes consumed less than 50 grams of carbs per day and had adapted to burning fat for energy. The goal of the study was to see how different types of carb intake would affect their endurance performance.
Participants tried four different routines:
- No carbs at all (placebo)
- A small carb drink 30 minutes before exercise
- Carb drinks for two days before exercise
- Carb drinks for two days plus a small carb drink right before exercise
Each person completed a 16.1 km cycling time trial under these different conditions.
What Were the Results?
Only the athletes who consumed a small carb drink 30 minutes before the trial showed improved performance. They finished the ride faster than when they had no carbs. On the other hand, eating carbs for two days before the trial did not improve performance.
Why Do Pre-Workout Carbs Help?
Even for keto-adapted athletes, a small dose of carbohydrates before exercise seems to help in several ways:
- Prevents low blood sugar: On a keto diet, the liver stores less glycogen, which means blood sugar can drop quickly during exercise. A small amount of carbs before a workout helps keep blood sugar stable.
- Boosts brain performance: Low blood sugar can affect the brain and make athletes feel tired or dizzy. Carbs may prevent this.
- Activates the brain’s reward system: Simply tasting carbs can trigger brain signals that enhance motivation and performance, even without fully digesting them.
Does This Mean Keto Athletes Should Eat Carbs?
Not necessarily all the time. The key finding is that strategic carb intake, especially just before high-intensity efforts, can be helpful. Athletes can stay on a low-carb diet most of the time but still benefit from a small carb drink 30 minutes before a competition or hard training session.
How Much Carb Was Used?
The pre-exercise drink had 60 grams of dextrose (a simple sugar). That’s about one medium bottle of a typical sports drink. This amount was enough to improve performance without kicking the athlete out of ketosis in the long term.
Key Takeaways
- Keto-trained athletes can improve endurance performance by consuming a small carb drink before exercise.
- Loading up on carbs over two days doesn't help as much as just having some right before a workout.
- The performance boost likely comes from stabilizing blood sugar and supporting brain function.
Final Thoughts
If you're an endurance athlete on a ketogenic diet, you don’t have to abandon your low-carb lifestyle to gain performance benefits. A small amount of carbs before intense efforts might be just what you need. Think of it as a targeted tool—not a cheat meal.