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.

What we've found so far is that a 5-day ketogenic diet may lower post-exercise blood glucose in endurance cyclists. The evidence we've reviewed also suggests this change in blood sugar levels might be linked to reduced performance, possibly because the body isn't managing glucose as effectively during recovery. Our analysis of the available research shows that cyclists following a short-term ketogenic diet had lower blood sugar after exercise compared to when they ate their normal diet [1]. This finding comes from one assertion based on 60.0 supporting studies, with no studies refuting this effect. While the number of supporting studies appears high, we are only working with one distinct claim at this point, which limits how much we can generalize. We don’t yet have enough detail on the study designs, sample sizes, or performance metrics to fully understand the strength or consistency of this effect across different conditions. We also don’t know how meaningful the drop in blood glucose is for overall recovery or long-term training outcomes. The evidence we’ve reviewed leans toward the idea that reduced glucose availability after exercise could interfere with performance, but we can’t say for sure how much this impacts real-world cycling outcomes like endurance, power output, or race results. Based on what we've reviewed so far, it appears that even a short ketogenic diet can influence how the body handles blood sugar after exercise. However, we don’t have enough evidence to say whether this change is consistently harmful, neutral, or possibly beneficial under certain conditions. Practical takeaway: If you're an endurance cyclist, a 5-day keto diet might lower your blood sugar after workouts — which could affect how you feel and perform. Pay attention to your energy levels and recovery if you try this.