To Train Fasted or Not?

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To Train Fasted or Not? 

Hand-in-hand with fitness comes the topic of diet. Everyone has different ideas and preferences on what they deem to be the best diet to accompany a fit and healthy gym-fuelled lifestyle, from high fat to low fat, meat-eating to vegetarian. A big point of discussion amongst the fitness community as of late is fasting - in particular, the idea of training fasted. 

Before you head to the gym on an empty stomach, consider whether this mode of working out is right for you, your particular body type, and your fitness needs. Both training fasted and not-fasted have their benefits and drawbacks, and it’s all about finding the right method for you. To help give you an idea, we’ll explore the benefits of each and what’s happening on a physiological level. ‍

What happens when you train fasted

First thing’s first, what is training fasted? In short, training fasted means you have not consumed anything of caloric value prior to training. The lines between ‘caloric value’ are a little blurred, with some camps saying you should consume zero calories while others believe minimal calories (e.g. 20) can still count as training fasted. 

It all comes down to how much energy you can ingest before your body recognise your intake as ‘food’ and commences metabolic pathways and digestion. There are some little-to-no caloric value foods that are considered fine to ingest to still be ‘training fasted’. These include black coffee, black tea (no sugar!) and some BCAAs (if they are very low in calories). Most people can consume these without their body seeing it as food intake. 

So why train fasted? The idea behind this method of training is that you force your body to use its stored glycogen (i.e. stored carbohydrate reserves) to fuel your workout. Carbohydrates are generally your body’s preferred source of energy fuel, and once your glycogen reserves have been used up during your training session then your body will start burning fat as its next choice of fuel. If your workout is intense enough and you’ve used up all your glycogen, then training fasted should have you burning more fat. 


Another benefit of training fasted is that it is thought to be easier on your gastrointestinal tract (i.e. your tummy). With less volume in your stomach when working out, there is less chance for potential discomfort while training. 

So what are the disadvantages to training fasted? For one, you may feel lethargic or tired while training as you haven’t had any food intake to help fuel you up for your session. This may mean that you’re unable to lift as heavy a load as you potentially could in a functional session, or not be able to run that 500 metre buy-out as fast as you would have liked. 

What happens when you train not-fasted

The other side of the debate is that you should always eat before training, and there are a few good reasons for that. As carbohydrates are the preferred source of fuel when exercising your muscles, consuming carbohydrates before a workout can help fuel your muscles up for optimal performance. This means that your muscles will have more capacity to work harder and stronger, for longer. 

Consuming (the right types of) food before a workout can translate to having an increased output, like doing a few more reps or lifting slightly heavier than when training fasted. Your brain may also have a perceived increase in capacity thanks to the carbohydrate intake, making you experience improved performance. The train of thought here is that if you have an increased capacity to work harder, the end result is that you may burn more energy compared to training fasted. 

Should you train fasted? 

It’s clear that a logic exists behind both methods of working out, whether it’s fasting or not fasting. Ultimately, it comes down to a matter of personal preference whether or not you want to train fasted. The best way to find out is to try both modes of fitness and compare your performance between the two. 

Some of us may experience decreased performance when training fasted while others may not notice a difference at all. Some may feel too dizzy and tired without eating before a workout while others feel more energetic. Trial and error is the best way to see which style suits you and your training schedule, so experiment a little and see what works for your unique body type.

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Written by

Claudia Cramer

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