How to Combine Intermittent Fasting with Intense Exercise

Intermittent fasting, particularly on a 16:8 schedule (fasting for 16 hours and eating within an 8-hour window), has gained immense popularity for its potential health benefits, including weight management and improved metabolic health. However, a common dilemma among intermittent fasters is how to approach their fasting regimen when faced with intense exercise either on the same day or the following day.

Should you adjust your fasting hours, skip intermittent fasting altogether, or maintain your regular eating schedule? In this article, we’ll delve into these questions, backed by research, to help you make informed decisions regarding intermittent fasting and intense exercise. To read more about what Intermittent Fasting is, click here. 

Intermittent Fasting and Exercise Timing

Integrating exercise with intermittent fasting can be a powerful combination for achieving fitness goals. Research suggests that exercising in a fasted state might enhance fat utilisation and improve metabolic flexibility, but it’s not suitable for everyone. If you prefer to exercise while fasting, aim for light to moderate activities like brisk walking or yoga during your fasting window. However, for intense workouts or extended runs (e.g., a 10km distance run), it’s advisable to fuel up first.

Pre-Workout Nutrition

Eating strategically before intense exercise can help you perform at your best and recover efficiently. If you plan to exercise intensely, consider breaking your fast with a balanced meal 2-3 hours beforehand. Include a mix of carbohydrates, proteins, and healthy fats to provide sustained energy. (If you are follow the Keto/Banting Diet, avoid carbs) This pre-workout meal can enhance your endurance and overall workout performance.

Post-Workout Refuelling

After an intense workout, your body needs nutrients to repair and recover. Fasting immediately after such activities may hinder this process. Hence, it’s a good idea to prioritise post-workout nutrition. Aim to consume a well-balanced meal rich in protein, carbohydrates, and essential nutrients within the first couple of hours post-exercise to aid muscle recovery and replenish glycogen stores. (If you are follow the Keto/Banting Diet, avoid carbs.)

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Adjusting Fasting Hours

Flexibility is key in maintaining intermittent fasting when intense exercise is in the picture. If you exercised intensely on a fasting day, consider shifting your eating window to allow for post-workout nutrition. For example, if your usual eating window is from 12 PM to 8 PM, and you work out at 9 AM, it may make sense to adjust your eating window to start earlier, say at 10 AM, to accommodate your post-workout meal.

The Rest Days Factor

On days when you plan to rest or engage in light exercise, you can adhere to your regular intermittent fasting schedule. This consistency can help your body adapt to the fasting routine and maintain metabolic benefits.

Hydration and Electrolytes

Staying hydrated is crucial during intermittent fasting, especially when combining it with exercise. Intense workouts can lead to fluid loss and electrolyte imbalances. Ensure you drink enough water and consider adding electrolyte-rich fluids or foods to your post-workout nutrition to prevent dehydration and muscle cramps.


Incorporating intense exercise into your intermittent fasting routine is entirely possible with some adjustments and careful planning. The key is to prioritise your body’s needs for fuel and recovery. Pre-workout nutrition, post-workout refuelling, and flexibility in your fasting window are essential elements to consider. On days of intense exercise, it’s advisable to adapt your fasting hours to accommodate these needs. However, on rest days or lighter workout days, you can stick to your regular fasting schedule.

Remember, there’s no one-size-fits-all approach, and individual preferences and goals may vary. Consulting with a healthcare professional or registered dietitian can provide personalised guidance tailored to your specific needs and fitness objectives. By finding the right balance between intermittent fasting and intense exercise, you can harness the benefits of both to optimise your health and fitness journey.

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