Intermittent Fasting – when is it ok to work out?


It is true to say that the benefits of Intermittent fasting (IF) are probably the worst kept secrets in the wellness world.  Few can doubt IF’s capacity to manage weight, give more energy, and clear up brain fog.


In recent years Intermittent fasting diets have exploded in popularity – from the Dr Michael Mosley endorsed 5:2 diet to the ‘two weeks on, two weeks off’ intermittent diet plan, to the more recent contender ‘one meal a day diet’ as expounded in the recently published How to Lose Weight Well diet by Dr Xand Van Tulleken, who says that:


“There’s a large amount of medical evidence that indicates that fasting is a safe and effective way of losing weight. Some researchers describe fasting as being a good kind of stress on your body, like exercise, and that it promotes fat burning.”


Despite IF’s benefits and trendy status, Fasting has actually been around for thousands of years.



  • It is known as the ‘Hunger Cure’ in Africa, where special kraals (huts) are set aside on the outskirts of villages for people to recover their health.


  • Knowledge about fasting was once widespread in the West, especially in the early schools of philosophy with the Stoics and Epicureans.  Even the Greek mathematician and philosopher Pythagoras used to instruct his students to fast before they received his higher teachings.


  • The great physicians of antiquity, such as Hippocrates, often made use of fasting methods too.


  • The practice also has special significance in the Old and New Testaments, particularly in the story of the Jesus’ temptations in the Gospels.


Intermittent Fasting

I was personally so impressed with the results of therapeutic fasts when I lived in India, (and this included an experience of living in a cave for ten days with nothing but pure spring water to drink…as you do) that I decided to devote the rest of my life to this method of healing.


These experiences inspired the development of the 12-Day Cleanse program, a type of IF, that incorporates a 3-day liquid diet intake during the power phase.  The main difference is that it is supported with supplements that help to accelerate the natural process of autophagy.


When is it ok to work out?


No matter how you approach IF, though, it definitely takes planning.  More so, if you want to make workouts happen, as my one-on-one clients require for example.


One of my clients who is an IRON MAN contender and holds down a big job in the city, recently asked me when exactly he should eat when he’s trying to fuel (and recover from) a workout?


I responded that it is okay to do up to 30 minutes of cardio when fasting, so this means that you can plan your workouts whenever you want but if you’re doing cardio for much longer than that, your body is going to rely on stored glycogen—sugar used for energy for intense activities—to fuel your workout and your performance may not be as good.


However, if you’re competing or trying to get a PB, a fed workout is always going to be better than a fasted one. You’ll feel a lot better and have better endurance because you’ll have full glycogen levels.  My Pro tip is to eat a small meal or snack anywhere between three hours and 20 minutes before your workout so your body has ready glycogen for fuel. This can be something like peanut butter on toast or an apple with nut butter, and if you’re avoiding carbs, it could be a yogurt (or alternative to yogurt) with nuts.


Ultimately it depends on what kind of sweat you are into.  It is always advised when practicing Yoga to practice on an empty stomach.  Eating is discouraged for anything up to two hours pre-practice, and 30 minutes afterwards.


However, if you’re doing weight training, scheduling workouts around your eating window is even more important. In this case, you should eat one to two hours both before and after your session. Make sure that your post-workout meal includes ample protein, to rebuild your muscles.


IF can take a bit of getting used to, but its biggest rule of thumb is nothing new: Listen to your body. If you’re hungry, it’s okay to eat.





In my workshop this Sunday Oneyogalondon “Intermittent Fasting + Kriya for Self Care”, we will be
looking at how fasting is the first principle of medicine; the practical steps of how fasting works, and its benefits, and how it has been used across cultures including in classical civilisation, with the Stoics and Epicureans. A few tickets remain. You can book here 🌝 🌙


For more tips on how to live a healthier lifestyle, check out my new book, which is available on Amazon, and all leading bookstores, including Waterstones and Borders.

‘Mind Body Cleanse’ by Chris James (Penguin Vermilion, £14.99). Available from here:

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