Is training fasted a good idea?

With so many mixed messages about nutrition before training sessions, it is not surprising that it can be confusing knowing what the best plan of attack is. So, is training fasted a good idea? Check out the ins and outs below.

Is training fasted a good idea?

The short answer to this question is a resounding ‘yes’, however it does come with a great big ‘but’ attached. The but relating to ‘but it depends on which session’. The most recent research shows that completing some training sessions fasted, or with low carbohydrate availability improves the body’s ability to use fat as a source of fuel, store glycogen, along with increased development of mitochondria in the cells. Mitochondria are often referred to as the ‘powerhouse’ of our cells, so more of them can mean better performance. However, it is not wise to complete all sessions this way, as we need to also be able to use carbohydrates well as a source for fuel; if we do all sessions fasted, this may blunt the bodies’ ability to do this. Mixing up our sessions to be fuelled, and fasted results in best performance.

So how do we pick which sessions to eat before, and which to not eat?

Our muscles store carbohydrates as a substance called glycogen. There is enough of this in well-fuelled muscles to last for approximately one and a half hours, depending on intensity of session and fitness level. The fitter you are, the more you will likely find you can do without fuelling before hand. This doesn’t mean you don’t need to fuel; it just means that your body is more efficient, and if you do fuel well, it is likely you will perform even better.

When to train fed?

As a general rule of thumb, fuelling up before training sessions is recommended in the following situations:

-       Long (more than 1.5hrs), endurance session that includes efforts

-       Higher intensity sessions more than 1 hour

-       Resistance training sessions

When to train fasted?

Fasted sessions, or those completed with low carbohydrate availability are best completed for low-moderate intensity sessions. Including some higher intensity sessions fasted is a good idea.

As an example:

Training day 1: 1 hour run, easy pace in morning + 2 hour hill session bike in the afternoon – morning session do fasted, afternoon session do fed.

Training day 2: 4 hour bike + 1 hour run in morning – do this long session fed

It is important you listen to your body, and individualise how this is incorporated into your training plan, due to differences in how well each individual responds to fasted sessions.

Chloe McLeod is the MX Endurance Dietitian and is available to answer all of our members questions.

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