The effect of heat and dehydration on carbohydrate use during endurance 🥵

The independent and combined effects of metabolism.

Tom Coughlin

Aug 26, 2025

Study Details

This new systematic review compiled data from 51 studies (502 participants) to establish the effects of…

🌡️ Heat stress

🥵 Dehydration

…and their combined effects on carbohydrate metabolism during endurance exercise 🔍

Here are the key findings ⬇️

Key Findings

Compared to temperate conditions (~ 20°C), hot conditions (~35°C) leads to higher…

🍞 Carbohydrate use

😮‍💨 Respiratory exchange ratio

🔥 Carbohydrate oxidation

🔋 Glycogen utilisation

Compared to being in a hydrated state, dehydration (~2.7% bodyweight loss) also leads to increased…

😮‍💨 Respiratory exchange ratio

🔥 Carbohydrate oxidation

🔋 Glycogen utilisation

However, studies suggest these increases are only present in hot environments 🌡️

(the effects are unlikely to be due to hydration status)

Conclusion

Dehydration does not appear to be a primary driver of carbohydrate metabolism ❌

However, if exercising in a hot environment ~35°C, carbohydrate use and therefore pre- / during / post-fuelling may need to increase 📈

Reference

https://link.springer.com/article/10.1007/s40279-025-02294-3

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