Do caffeine fasts work?

21. July 2020

Some athletes go caffeine-free in the run-up to a competition, hoping it will increase the stimulant effect when it really counts. But does it actually improve performance?

The benefits of caffeine for sporting performance are widely recognised. Caffeine has a stimulating effect that peaks around 30 to 90 minutes after taking it, and reduces perceptions of fatigue, stress and pain. On top of that, caffeine acts on muscle cells, increases the body’s ability to absorb carbohydrates and improves fat oxidation. These effects are especially pronounced during:

  • Endurance activities lasting over 20 minutes
  • High-intensity activities lasting 1 to 20 minutes
  • Activities with high-intensity intervals (e.g. team sports)
  • Maximum-intensity training

Caffeine has become well established as a way to boost sporting performance. It is usually taken before (ideally around 40 to 50 minutes before the start) or during a competition in the form of coffee, tablets, gels or sports drinks. Athletes often also take some towards the end in the form of (well-shaken) cola. On top of that, many athletes also cut out caffeine completely in the run-up to a long competition, so as to boost its effect during the event itself. But what benefits is that supposed to have?

The thinking behind it seems logical enough. Regular coffee drinkers who’ve had a night without much sleep will feel in the morning that they won’t be able to get the day off to a good start until they’ve had a coffee. Going without caffeine for a few days before a competition will strengthen this feeling and make the coffee’s effect more potent, or so the idea goes. This would mean that caffeine has a stronger effect on people who don’t consume it regularly.

Abstaining from caffeine doesn’t increase its effect

To test this hypothesis, the University of São Paulo conducted a study with well-trained male cyclists, who had to complete three time trials of around 30 minutes in duration. Before the test, they were given either caffeine (6 mg/kg of body weight), a placebo or nothing. The result? The cyclists who took caffeine performed best, with a 2.4% lead over the placebo group and 3.3% over the group who didn’t take any tablets at all. The improvement in performance due to caffeine was highest for the group with a moderate daily caffeine intake, and lowest for those with a lower intake. This appears to show that how much caffeine someone normally consumes has no effect on the performance-boosting effect of caffeine.

Other studies have corroborated this result: caffeine’s performance-boosting effect isn’t improved by abstaining from caffeine beforehand. This suggests that going caffeine-free ahead of a competition doesn’t improve measurable physical performance, but instead gives a mental boost.

In conclusion

If caffeine fasting puts you in the mindset for top performance, then go for it! But you should always do a trial beforehand to check how well you cope. Regular coffee drinkers who go cold turkey often have bad reactions like headaches, nausea or low energy. Getting these negative side effects right before a competition can far outweigh the additional subjective boost you might potentially get from taking caffeine after a period of abstinence.