Caffeine activates and carbohydrates stabilise fat metabolism

Koffein aktiviert und Kohlenhydrate stabilisieren den Fettstoffwechsel

Caffeine and fat oxidation – current scientific understanding 

Since the 1970s, scientists have debated whether caffeine enhances fat oxidation. Recent studies, including the work of Ruiz-Moreno et al. (2020), confirm that caffeine can increase fat oxidation by around 27 %, though only under specific conditions. 
 
In this study, trained participants consumed 3 mg of caffeine per kilogram of body weight one hour before completing a one-hour cycling session at moderate intensity.

Results:

  • 24.7 grams of fat were oxidised with caffeine. 
  • 19.4 grams under placebo conditions. 

This means greater fat oxidation, but not higher total energy expenditure – the additional energy came from fat rather than carbohydrates. 

Why this does not automatically lead to fat loss 

More fat oxidation does not automatically equal fat loss. Body fat is only reduced when energy expenditure exceeds energy intake. The increase caused by caffeine corresponds to roughly 5 grams of fat per hour – meaning around 200 hours of training would be needed to burn 1 kilogram of body fat. 
 
The effect is metabolically interesting but not a quick fix for weight loss. For endurance athletes, it can be relevant, as regular phases of increased fat oxidation can, over time, train fat metabolism and reduce glycogen dependency. 

Carbohydrates do not block fat metabolism 

It was long assumed that consuming carbohydrates during exercise would suppress fat metabolism. A recent study by Nybo et al. (2022, Int J Sport Nutr Exerc Metab) demonstrates the opposite: even when consuming 60–120 grams of carbohydrates per hour, fat oxidation remains active – especially during long or intensive sessions. 

Key findings:

  • During prolonged exercise, fat and carbohydrate metabolism run in parallel.
  • Carbohydrates ensure consistent energy availability and prevent the body from down-regulating performance.
  • This keeps total energy expenditure high – and although the relative proportion of fat may decrease, the absolute amount of fat burned actually increases.
  • The combination of caffeine and carbohydrates can even enhance fat oxidation, as caffeine increases fatty acid release and oxidation rates. 

Caffeine and carbohydrates – finding the optimal balance 

Caffeine mobilises fatty acids, carbohydrates provide stable energy – together they create a synergistic effect. This combination is particularly effective at moderate intensity (around 50 % VO₂max) or during the middle phases of long endurance sessions. 
 
Practical recommendations:

  • Take 3 mg of caffeine per kilogram of body weight about 60 minutes before training.
  • Consume 60–90 grams of carbohydrates per hour to support both performance and fat metabolism.
  • Ideal option: CAFFEINE GEL 40.

Note for winter: Insufficient carbohydrate intake – especially during so-called fat metabolism training – can weaken immune function and increase susceptibility to infections. An adequate energy supply protects the body and supports both recovery and immune defence. 

Conclusion 

Caffeine can measurably stimulate fat metabolism, particularly at moderate intensity and in a fasted state. While carbohydrates were once thought to inhibit fat metabolism, it is now clear that they sustain performance, maintain total energy turnover, and can even enable greater absolute fat oxidation. 
 
The best strategy: use caffeine strategically, adjust carbohydrate intake to your needs, and test both regularly in training. 

References 

  • Ruiz-Moreno, C., Gutiérrez-Hellín, J., Amaro-Gahete, F. J. et al. (2020). Caffeine increases whole-body fat oxidation during 1 h of cycling at Fatmax. Eur J Nutr. https://doi.org/10.1007/s00394-020-02393-z 
  • Nybo, L. et al. (2022). Carbohydrate intake during exercise does not impair fat oxidation. Int J Sport Nutr Exerc Metab, 33(2): 112–125. 
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