Why Fasted Training is 'Fast' Becoming Outdated

Fasted training used to be popular amongst both recreational and elite athletes. However, as more is understood about its impact on the body (and performance), that popularity is waning. Renee McGregor explains why fasted training is becoming outdated

A few years ago, the term fasted training was on everyone’s lips - from elite athletes to recreational. While some endurance athletes still participate in this type of training, the majority are moving away. So, why have so many of us become disillusioned with fasted training?

What does the science say?

Before we completely dismiss fasted training, it is important to state that there is evidence to suggest that doing some training in a carbohydrate-depleted state can help you utilize more fat for fuel which could be an advantage - particularly in endurance events where our glycogen stores become depleted and a limiting factor. We know that with moderate intensity, our stores can last around 90-120 minutes. The theory is that if we help our body to adapt to utilizing more fat as fuel then we can spare our glycogen stores for longer. 

RELATED: Is Sports Nutrition All It's Cracked Up to Be?

This concept is also known as “training low” and was first used in long-distance road cycling. However, as often is the case, scientific evidence gets misinterpreted, reworded, and repackaged into something that is not strictly true, but usually be a way to generate financial gain for someone. 

Fasted training/ training low is no exception to this rule and a bit like a game of whispers, it has gone from training in a carbohydrate-depleted state, to encouraging individuals to maintain low carbohydrate intakes at all times. 

What the science states is a little different. Training low does indeed involve training in a carbohydrate-depleted state, which is why many prefer to do this first thing, and thus has become known as fasted training. BUT, and it’s a big but, it does come with some key protocols if an individual is to truly benefit. 

Firstly, these sessions should only be done twice a week maximum. Secondly, they should ideally only be up to 60 minutes long and at an intensity that is no higher than 60% of your vo2 max of 6/10 perceived exertion. Finally, and most importantly, you should still consume your overall carbohydrate requirements after training, distributed evenly throughout the rest of the day. This final point is critical to get adaptation from training. Indeed, a meta-analysis of studies by Mata et al, 2019 showed that if an individual consumed a low carbohydrate intake for 3 weeks or more it started to have negative consequences on performance and also health. 

DID YOU READ? Why You Should Avoid Fasted Training

Studies from Loughborough University by Professor Gleeson have demonstrated repeatedly that low carbohydrate availability often results in a depressed immune system. In addition, recent research has highlighted that completing too many fasted training sessions, and particularly doing long or high-intensity training in a fasted state, can cause our stress hormone, cortisol, to rise. If this becomes chronically raised, the hypothalamus in the brain picks up that the body is under stress and thus threat. This can then lead to a downregulation of hormones across the body resulting in poor metabolism, poor adaptation from training, storing more fat within the body, and a higher risk of injury and illness to name a few consequences. 

So, It is easy to see why we are fast falling out of love with fasted training, particularly when those original claims about how it has a huge benefit in those who complete endurance activities do not stand up. In fact, it would seem that the reverse is true. 

RELATED: Eat Healthy! Five Delicious Evening Meal Ideas for Athletes

What about if it is too early to eat?

For many endurance athletes, fasted training is just a convenience. They like to train first thing before work and the lack of available time can make it challenging to consume energy before training. 

However, it is becoming clear that fueling our morning training is not only advantageous for our health but also for our performance and body composition. So how do you go about optimizing your training with appropriate fueling before an early morning session? 

Some good examples of easily digestible fuel include:

• Hot cross buns

• Glass of fruit juice and banana

• Slice of toast

• 1 Weetabix with milk

• Fruit yogurt

• Sports gel

Therefore, making sure you take on some carbohydrate pre-training and then recovering post-training with a good combination of carbohydrate and protein - ideally within 30 minutes - will ensure optimal adaptation and progression, as well as encourage a consistent approach to training.