Intermittent fasting has grown a lot in popularity among athletes from its rising presence on social media promoting weight loss, reduced inflammation and an extensive range of other health claims. However the question still remains, is this actually beneficial for athletic performance?
What is intermittent fasting?
Intermittent fasting is when you shorten the time window in the day where you eat food. This lengthens the amount of time that your body goes without food, putting it in a ‘fasted’ state. There are a range of different types of fasting protocols that you could follow, the most common being:
- The 5:2 diet: 5 days of normal eating followed by 2 days of restricting calories (restricted to about 500-600 calories per day)
- The 16:8 diet: Eating within an 8 hour window and fasting for 16 hours each day
- Alternate day fasting (ADF): Alternating days of eating and fasting (it can either be a complete fast or restricting to 25-30% of your total energy requirements)
- Time restricted eating (TRE): Fasting for 12-20 hours per day, with an eating window of 4-12 hours – you choose
It is important to remember that our bodies are naturally put into a state of fasting every day when we sleep!
How will it affect your body?
The impact of meal timing around an athlete’s training is known to have an impact on how well they can perform. When the body goes into a state of fasting, it maintains its energy levels by switching the primary source of fuel from carbohydrates to fats. This promotes ketosis in the body, similar to the ketogenic diet. Because of this, intermittent fasting may be useful for athletes that need to lose weight, however, it may have impacts on their performance.
What are the benefits?
Intermittent fasting can help individuals to manage their weight by providing a structured and simple approach. Theoretically, less food is consumed over the day leading to weight loss.
New research shows that intermittent fasting in combination with aerobic exercise and resistance training may reduce body fat without impacting fat free mass (water, bone, muscle and tissue) – all of the important stuff to maintain for optimal performance!
While this all sounds pretty positive, there are definitely things athletes need to consider before starting intermittent fasting.
What are the challenges with intermittent fasting?
A really common challenge that athletes face is overeating due to hunger and feelings of deprivation, potentially causing binge eating and excessive snacking, especially at night.
If not done properly, fasting might make it hard to maintain muscle mass, making it less suitable for athletes. Another challenge is the possibility of developing low energy availability, as adequate energy availability is crucial for performance.
Constantly feeling hungry and deprived of nutrients can impact daily activities, causing drops in blood sugar, dizziness, and even fainting. Unintentional weight loss from restricted eating windows may also occur which can negatively impact performance, especially in sports where weight loss is not favorable.
Studies also show potential disruptions to athletic performance, including slower sprint times, decreased peak power output in cyclers and impaired endurance in high-intensity, aerobic sports.
Is it right for you?
If you’ve considered intermittent fasting here are some questions to ask yourself before you start:
- Do you have any medical conditions that may be impacted by fasting?
- Are you showing up to training with energy?
- Are you hitting PBs in the gym?
- Have you been losing muscle mass?
- Is your body taking a longer time to recover?
- Are you able to eat enough calories in a shorter eating window?
- Does your sport have a weight-class or body composition requirement that could be impacted by fasting?
- Is your mood, concentration or sleep quality affected by fasting or feelings of hunger?
- Will fasting allow you to maintain adequate hydration?
Practical tips on how to implement intermittent fasting safely for your sport
If you’ve decided intermittent fasting is something you would like to try, here are some practical tips on how to implement it safely:
- Firstly, and most importantly, pick an approach that suits you
- Time it around your training schedules. For example, if you train at a high intensity in the morning, think about moving your feeding period to earlier in the day. This way, you will be fasting in the afternoon when your body may not require as much energy
- Ensure you are maintaining some sort of resistance training routine to avoid the loss of lean muscle mass
- Maintain adequate protein and carbohydrate consumption
When it comes to athletic performance, the challenges of intermittent fasting may outweigh the benefits. Limiting the timeframe for eating may increase the risk of developing low energy availability, leading to a decline in performance. Ultimately, when considering intermittent fasting, athletes must carefully reflect on their goals – whether prioritising performance or physique based outcomes – and tailor their nutrition strategies to their individual training load, recovery needs and overall well being.