Can sugar mouthwash help you bike faster on a no-carb diet?
Carbohydrate mouth-rinsing does not rescue simulated time trial performance in trained endurance cyclists following a 5-day ketogenic diet
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Ketone levels didn’t predict how badly someone performed on keto.
Many believe higher ketones mean better fat adaptation and performance, but here, some with high ketones still performed poorly — showing ketosis ≠ performance readiness.
Practical Takeaways
Avoid going keto in the week before a race or intense endurance event.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Ketone levels didn’t predict how badly someone performed on keto.
Many believe higher ketones mean better fat adaptation and performance, but here, some with high ketones still performed poorly — showing ketosis ≠ performance readiness.
Practical Takeaways
Avoid going keto in the week before a race or intense endurance event.
Publication
Journal
Journal of the International Society of Sports Nutrition
Year
2025
Authors
Guy Guppy, James Brouner, O. Spendiff
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Claims (6)
Cyclists on a keto diet for 5 days had high ketone levels, but that didn’t really affect how well they performed — so ketones alone might not tell us much about performance at the start of keto.
Cyclists who eat a keto diet for 5 days have lower blood sugar after exercise than when they eat their normal diet, which might make them perform worse because their body isn’t managing sugar as well.
Going on a keto diet for just 5 days makes elite cyclists slower in time trials, adding about 3 more minutes to their ride time.
If cyclists on a low-carb diet rinse their mouths with a sugary drink every 7 km during a 21-mile ride, it doesn’t actually help them finish faster compared to rinsing with a fake sugar drink — their mouths might taste sugar, but their bodies don’t get the boost.
Swishing carbs in your mouth during a ride doesn’t raise your blood sugar if you don’t swallow them — at least in well-trained cyclists.