How I use fasting to get the most out of my exercise

I get teased a lot (mostly by my wife) for “always telling everyone that you’re fasting today.”

That’s because I get a kick out of pushing controversial buttons. Fasting is an interesting topic and I’m always met with a common refrain: “I heard that fasting isn’t good for you” or “watch out, you’ll have a hypo.”

It’s okay if you have the same questions. I’m here to push the controversial buttons with the goal to shed some light on how fasting can be a very useful tool to get the absolute most out of your exercise routine.


Why should I want to get the most out of my exercise?

Time is precious.

Why should you go to the gym, or go for run or play a game of basketball and not get the most benefit out of that? Even though I am an Exercise Physiologist, exercise itself can often feel like a chore. In my experience working with clients, it’s not just the case for me. Most people quickly sacrifice exercise if they are short on time or have more important things to do.

That’s the rationale for maximising what you get out of your exercise session. You get more out of your time. Invest 30 minutes, get a maximum return on your investment of time.

Keep in mind that my main goal right now is to get fat out of storage and reduce my body fat %

An analogy to help illustrate the benefits of fasting

Let’s say that you have a basketball game in 2 hours (yes, I actually have a basketball game to play in 2 hours 😂) and you decide that you need to fuel up. So you quickly eat 2 bananas as a pre-game meal.

Over the ensuing 2 hours, your stomach will break down the 2 bananas and release the macronutrients into the blood available for use. Bananas primarily consist of carbohydrates which get digested into sugar and released into the blood.

Once you get to your game, warm up and play, your body will first use the sugar that is already in the blood (this is one of the main roles of insulin – to ensure that blood sugar is used up first by active muscles).

If you use up more energy than you consumed through external sources (food/drinks etc) then your body will go and use the previously stored sugar (glycogen that’s stored in the liver.)

Then, if you still require more energy to get through your game, your body will start to use your stored fat to fuel your muscles during the game.

How I use fasting to help me lose fat

Following from the analogy above, if you enter the basketball game on a prolonged fast (more on the specific details later) your body experiences a gradual lowering of blood sugar which forces the stored sugar (glycogen) to be used up earlier.

As a result, you may already be burning stored fat before you start the basketball game.

Now, every bit of energy that you need to get you through the game should come from stored fat. The more you run/jump the more energy your body burns, the more stored fat your body will use up.

This analogy is literally what I do. It’s what I am doing right now as I write this.

Here is a video that I recorded a few years ago demonstrating the effects of the fast on my blood sugar

How to use fasting before exercise – specific instructions

Who can benefit from fasting?

  • If you want to lose fat
  • If you don’t have the time to exercise very often (<1 hour per day)
  • If you have a family history of diabetes

Who should not be fasting?

  • If you are injecting insulin

How long to fast before exercise?

  • In order to boost fat burning, you should be fasted for at least 16 hours prior to your exercise bout.

What can I have during my fast?

  • Water – as much as you like, it helps keep you from feeling hungry too
  • Black coffee – avoiding coffee is ideal but having a black coffee is okay and won’t affect your fat burning
  • Black tea or green tea – no added sugar or milk. Same as coffee in that it’s better to avoid it but it won’t hurt to have tea.

What if I get really hungry?

The first few times you do an extended fast will result in hunger, but the feeling of hunger eases the more you practice as your body can flip into fat burning mode quicker and easier.

If you feel extremely hungry and cannot handle it try to have as little as possible to satisfy your hunger. Some of my favourite ideas are:

  • A small handful of nuts
  • Protein shake

The main thing is not to consume anything with sugar or carbohydrates in it.

When can I break my fast after exercise?

Usually I look forward to a great meal after I finish my exercise. In a perfect world, the longer you wait the better but my recommendation is to eat 30 minutes after exercise.

What can I eat to break my fast?

It doesn’t really matter and if you’ve completed a big fast and a good exercise session then you don’t need to be too picky. Protein is the most important macronutrient to consume after exercise. There is benefit to avoiding carbohydrates after exercise as well in order to maximise fat burning, but there is less emphasis on avoiding carbs after you exercise.


Other important notes:


Most people consume most of their salt intake from carbohydrates. If you are fasting, you might be low in salt which means that your body does not retain as much water as usual. This can cause dehydration if you are exercising or in warm weather.

My best tip is to add some salt to your water before you exercise. This will help reduce the chance of dehydration and also prevent cramping.

Dehydration is indicated early by a dull headache or light headedness. If you feel that then quickly get some salt into you and you should feel it improve quickly. 

Complicated health conditions

I have yet to see a client where fasting has failed to benefit from fasting (unless they are injecting insulin and I would never suggest fasting for them). However, doing anything new for the first time has it’s own risks. So if you suffer from a complicated health condition then it’s best to test fasting out in a controlled, monitored environment. Consult your health practitioner and let them know what you’re plan is. You can also contact us to get our opinion on your specific case.



  • Fasting can be a useful tool that helps you get more out of your exercise session
  • Fasting is especially useful for those who are wanting to lose fat
  • Fasting helps get the most out of your time if you aren’t able to exercise regularly
  • Fasting usually involves 16 hours without external calorie intake
  • It is okay to consume water, coffee and tea when you’re doing a fast
  • After exercise it’s important to consume protein but you can generally get away with eating what you want after exercise
  • It is best to wait 30 minutes after exercise to eat but not completely necessary
  • Dehydration is one issue associated with fasting. You can reduce your risk of dehydration by adding salt to your water before you exercise and looking out for the warning signs of headache and light headedness
  • If you have a complicated medical condition you should get your health practitioner to help monitor you or let you know if you should be avoiding fasting as a strategy


Feel free to write your questions in the comment box below. You can also chat with us using the chat icon in the bottom right corner. We love talking about how you can improve your health!

About The Author

Hany is an Exercise Physiologist & the Clinic Director here at Activate Clinic.

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