Can fasting improve your sports performance?

Yes, under specific circumstances. Many athletes schedule 5 Day Fast during a quieter training period, from endurance athletes to athletes in hybrid disciplines like Hyrox. How it fits in with your training and recovery varies from person to person. These benefits are mainly linked to the body's ability to use fats as a fuel source, metabolic sensitivity, and recovery. However, these effects don't happen during the programme itself, but mostly in the period after it.

How does 5 Day Fast affect your body and energy systems?

During the 5 Day Fast programme, your body gradually shifts from a metabolism that mainly relies on carbohydrates and quick energy sources to a state of ketosis, where fats become the main fuel source and your body also starts producing ketones as an energy source for your brain.

This shift goes hand in hand with several adaptations:

• greater metabolic flexibility

• improved insulin sensitivity

• mitochondrial adaptations

These effects are extensively described in scientific literature on fasting and energy restriction (1).

Research into protocols based on energy restriction also shows effects on metabolism and on cellular recovery processes (2).

These adaptations are especially relevant for endurance athletes, but also for athletes where energy efficiency, recovery, and long-lasting effort play an important role.

Fasting and sport: what does the science say?

In sports where endurance plays an important role, better fat burning helps to better preserve carbohydrate stores, the body's quick energy source. This can improve energy efficiency and delay fatigue during prolonged efforts.

Several studies show that strategies based on energy restriction or fasting can stimulate these metabolic adaptations (3) (4).

In practical terms, this means that an athlete who develops this capacity:

• uses fat more efficiently

• preserves carbohydrate stores better

• can sustain a steady effort for longer

These changes can also translate into better cardiovascular efficiency, with a lower heart rate at the same intensity, which is an important indicator of sports performance.

Together, these effects can indirectly support sports performance during prolonged efforts.

Research into energy restriction also looks at recovery processes and inflammatory markers (2). What that means for athletes' recovery isn't entirely clear yet.

The 5 Day Fast pack contains seven supplements, including Omega 3.

When should you plan 5 Day Fast (and when not)?

Timing is the most important factor.

A programme like 5 Day Fast acts like a metabolic reset, but the benefits only show up once normal eating and training have resumed.

When should you start 5 Day Fast? Generally, we suggest starting the 5 Day Fast programme 2 weeks before a race if you've got experience with fasting or with 5 Day Fast itself. For less experienced athletes, a period of 3 to 4 weeks before a competition is usually wiser.

As a more experienced athlete, you'll then finish at the latest 9 to 10 days before your race. That offers a better combination of recovery, replenishing energy stores, and supporting sports performance. If you have less experience, take a bit more time between finishing 5 Day Fast and your race. That way, you can be sure you recover properly and line up at the start fully rested and replenished.

Why?

Because your body needs time to:

• fully replenish carbohydrate stores and quick energy sources

• return to an optimal training load and intensity

• stabilise the metabolic adaptations

So make sure you plan enough time after the programme to gradually build up your eating and training again.

How do you plan the programme around your training?

However, timing alone isn't enough. The circumstances under which the programme is used are also important.

5 Day Fast is best fitted into a low-intensity training week, where training is maintained but high-intensity efforts are avoided.

The aim is to:

• limit physiological stress

• prevent excessive fatigue

• support metabolic adaptations

When used in this context, it can help to:

• optimise energy production

• support recovery capacity

When can it decrease performance?

When poorly applied, this type of protocol can negatively affect performance:

• starting within 10 days before your race → insufficiently replenished carbohydrate stores and recovery

• jumping back into high-intensity training too quickly → reduced performance

• during periods of high training load → excessive physiological stress

• not immediately integrating proper nutrition after the programme → loss of benefits

Which athletes is this relevant for?

5 Day Fast is particularly suitable for:

• athletes with a specific sport or fitness goal

• athletes who also want to optimise their nutritional strategy and general health

• athletes who can plan the programme smartly before their race (2 to 4 weeks in advance)

On the other hand, it's not recommended:

• in the week of a race

• when experiencing severe fatigue or an energy deficit

• in situations with increased recovery needs, such as injuries, high stress, or illness

• during pregnancy or breastfeeding

Are you taking prescribed medication? Always consult your treating specialist first.

Is 5 Day Fast a good strategy for endurance athletes?

5 Day Fast isn't a miracle cure, but a physiological tool.

When used correctly, it can support key mechanisms involved in sports performance, especially energy efficiency and metabolic flexibility. When applied incorrectly, it can actually hinder progress.

The key lies in a gradual integration within a broader training and nutritional strategy.