Intermittent fasting: good or bad idea for athletes?

Intermittent fasting is attracting increasing interest, even among athletes. Loss of body fat, improved concentration… There are many promises. 

But is this method really suitable for regular and/or intense use of Kinomap?

1- What is intermittent fasting?

Intermittent fasting consists of alternating periods of fasting (without eating) and periods of eating.

The best-known formats:

• 16/8: 16 hours fasting, 8 hours eating.

• 5:2: 5 normal days, 2 days with very little food.

• OMAD (one meal a day): only 1 meal a day

The aim is not necessarily to eat less, but to eat in a shorter time frame.

2- What are the benefits for athletes?

On the benefits side, various studies suggest that intermittent fasting can:

• Promote the loss of body fat while preserving muscle mass, provided that protein intake during meals is sufficient.

• Improve sensitivity to insulin (the hormone that allows glucose to be used as an energy source), which helps with carbohydrate management and recharging muscle reserves.

• Improve concentration: some sportsmen and women report better concentration when training on an empty stomach, particularly in endurance disciplines (running, cycling, etc.).

• Provide anti-inflammatory and regenerative effects, beneficial for recovery.

3- What are the limits of intermittent fasting?

Intermittent fasting is not without risks and side effects, especially for athletes and people who are very active on Kinomap.

Reducing energy availability can be detrimental to performance, especially in endurance or high-intensity sports. When training on an empty stomach, the body may lack the energy to sustain the effort, which impacts physical capacity (reduced performance), concentration, and recovery.

When training on an empty stomach, the ideal is not to exceed 45 minutes to 1 hour of low-intensity exercise.

In addition, a reduced eating window can make it difficult to meet recommended daily nutritional requirements. An inadequate intake of macronutrients (carbohydrates, proteins, fats) and micronutrients (vitamins, minerals such as iron or magnesium) can ultimately affect health, sleep, or hormonal balance (particularly in sportswomen).

Delaying food intake after a Kinomap session compromises the rebuilding of muscle glycogen (a form of carbohydrate stored in the muscles and liver) and therefore recovery.

In summary, the negative effects can be:

• A drop in performance

• A risk of deficiencies or undernourishment

• A negative impact on recovery

• Significant fatigue, irritability, and hormonal problems

4- Is intermittent fasting suitable for all sportspeople?

Intermittent fasting can be effective for sportspeople who want to lose body fat while maintaining muscle mass. It is best tolerated during periods of low training load, or when Kinomap sessions are scheduled during the eating window (see 1. What is intermittent fasting?).

On the other hand, it is not very compatible with a period of preparation for a competition or with a high volume of training.

To sum up, intermittent fasting is:

Yes if:

• The aim is to lose body fat without aiming for sporting performance

• The training load is moderate and well planned

• The protocol is well supervised and respects nutritional requirements

• Fasting is well tolerated (no fatigue or digestive problems)

No if:

• The aim is to build muscle mass or improve sporting performance

• There is a high energy expenditure (e.g. intense endurance sport), which is difficult to compensate for in a reduced eating window

• There is a history of eating disorders or an already stressed metabolism (illnesses)

Intermittent fasting can be a useful tool for certain sportspeople, provided it is properly supervised. It is not suitable for all profiles or for all periods of training and life. Listening to your body and eating a balanced diet remain two essential elements.
Before trying intermittent fasting, it’s important to seek advice from a health professional or sports nutritionist!

Chloé Masson
Nutrition Project Manager
chloemasson.nutrition@gmail.com

See previous nutrition articles :
DIET AND SLEEP
ANIMAL PROTEINS AND VEGETABLE PROTEINS
EATING WELL AFTER A WORKOUT