What is a fasted workout?

A fasted workout is any exercise that is performed on an empty stomach or after a period of fasting, usually overnight.

What are the claims surrounding this exercise habit? (e.g. increases metabolism, burn more calories, improve performance?)

It has been hypothesised that training while fasted may result in the following:

  • Increased fat utilisation by improving the enzymes involved with the breakdown of fatty acids to be used as energy by the body.
  • Increased insulin sensitivity due to the fact that insulin levels are low in a fasted state. Better insulin control is associated with a greater ability to burn fat.
  • Increased protein synthesis (creation of new proteins) as there is a bigger release of growth hormone and testosterone in the fasted state. Protein synthesis is essential for muscle growth.
  • Lead to reduced body fat, greater lean mass and better health, due to a combination of the points above.

Is a fasted workout more beneficial for weight loss and muscle building? Why/why not?

It has been hypothesised that performing aerobic exercise when fasted forces the body to rely on using fat as a substrate rather than carbohydrate, thereby reducing body fat to a greater extent than performance of exercise after food consumption. Some studies have shown this to be true while other studies have shown that long-term fat loss is not necessarily affected by whether or not an individual is fasted prior to training.

In regards to training for building muscle, a fasted state has been shown to increase growth hormone release, which helps the body make new muscle tissue as well as burn fat and improve bone density. In addition to growth hormone, fasting also elevates the release of testosterone, which is essential for increasing muscle mass and reducing body fat, as well as boosting energy levels and libido. This alone, might be enough to make some people want to try this method of training, however, it’s important to note that everyone’s circumstances are different. There is more than just one factor of fasting that plays a role in one’s ability to lose fat mass or build lots of lean muscle. Things like your environment, your genes, hormones, sleep hygiene, stress diet and exercise program all play a role, so when deciding on the best type of training that is most suitable to you, it is pivotal to include your health professional, trainer and even GP.

What advice would you give to people who exercise in the morning? 

If you train in the morning and are wanting to try the fasted training method, it is important that you are well hydrated. Overnight, your body is prone to dehydration, which may impact negatively on exercise performance. Consuming water is a great way to remain hydrated and still follow the principles of fasted training.

Some people may find training on an empty stomach tough, especially at first. It may take some time getting used to and it depends on the type of training you are doing as well as your base nutrition.

If you’re someone who has a fast metabolism, then you may need a little snack. An option is to have a protein and fat based snack before training or have sip on a protein drink during the workout. Branched chain amino acids (BCAA’s) are also great for maintaining muscle mass, as they are used by the muscle for energy.

How can we ensure we are fuelling our body properly before and after a workout?

The best way to think about pre- and post-workout nutrition is that one is fuel and the other is repair.The primary goal for eating before your workout is to ensure you have enough energy to push and exert yourself during a training session, and the main goal of the snack or meal afterwards is to repair the damage done to your muscles, and help them rebuild faster and grow. Depending on your goals, you can apply either or both, or you avoid them completely.

It doesn’t matter if your goal is fat loss or muscle building, your recovery or post-work out nutrition should be the same and the most important focus. To guarantee you are replenishing your glycogen stores appropriately and supporting muscle recovery and growth, it is important to make sure your post-workout meal/snack is consumed within 30 minutes of completion and contain at least 15-25 grams of quality protein (more is required if the recovery snack consists of plant-based protein) and approximately 1 gram of carbohydrate per kilogram of body mass.

Depending on the type and intensity of the exercise performed, your post-workout food choices should generally:

  • Be rich in quality carbohydrate to replenish muscle fuel stores
  • Contain some lean protein to promote muscle repair
  • Include a source of fluid and electrolytes to rehydrate effectively

It’s important to note that sometimes wholefood meals aren’t always practical, especially for those who aren’t hungry immediately after exercise. In these situations, consuming a liquid form of nutrition that contains rapidly digesting carbohydrates and proteins may be better tolerated as well as more rapidly digested and absorbed. However, think about saving your post-workout drink for weight training, interval, and endurance training lasting 45 minutes or longer. Lighter and casual exercise like walking the dog or riding your bike to the shops does not require a recovery drink.

In regards to pre-work out nutrition, a pre-workout snack is simply an aid to help to provide your body with fuel to help you move faster and perform better. If your goal is fat loss then this is not a necessity and you can easily schedule your workouts around breakfast, lunch or dinner so you don’t require a pre-workout snack. Also, if your session is only going to last 30 minutes then you are unlikely to need any special pre-workout boost. But if your training is going to be over an hour and performed at high intensity, then a pre-workout snack might be a good idea.

A small snack 1-2 hours before your training can help with a final top up of your fuel stores and is still enough time for the food to be digested without causing stomach discomfort or upset. Everyone is different in what they like to eat before exercise but in general, a pre-exercise meal or snack should be:

  • Rich in carbohydrate to prime your fuel stores
  • Low in fibre, especially if you have issues with stomach cramping or upset
  • Easy to digest – avoid foods high in fat as these are slow to digest

Bottom line: There’s no one “best” pre-exercise meal or snack option and it will depend on what your individual goals and requirements.