Should I Train Fasted?!
Fasted training is an area that can cause some confusion. Should you do it? If so what type of training should I do? Is it going to result in muscle loss?!
As with pretty much everything in performance nutrition fasted training is all about context! Here we’re going to dive into what fasted training actually is, bust some common misconceptions then dive into when it’s worth doing and of course HOW to do it.
What Is Fasted Training?
Simply put, it’s training after a long period of not eating (a fast), ideally to put your body in a state of low carbohydrate availability. There are several ways to do it but it’s most commonly carried out in the morning as this is just easier to do after an overnight fast.
But why do it?!
We know full well that for MOST sports carbohydrate availability is a huge limiting factor of performance, so why would we want to do this to ourselves?
The answer lies in creating physiological adaptations.
It has been shown that carrying out endurance training with low carb availability can AMPLIFY the adaptations such as increased mitochondrial biogenesis and improved aerobic enzyme activity.
It’s also been shown that fasted training increases fat oxidation which could play a role in becoming more metabolically flexible (the ability to switch fuel usage from carbs to fats depending on exercise intensity). This is useful for longer duration exercise such as endurance exercise but it can also be beneficial for things like CrossFit as we can recover quicker between workouts and spare muscle glycogen in longer workouts.
But people also perform fasted training as a method of accelerating fat loss. While its true training fasted can increase lipolysis this does NOT equate to loss of bodyfat.
See with science comes misinterpretation....
In the realm of fasted training, many people have misinterpreted the evidence around fat oxidation.
We know that fasted training can improve the efficiency of fat oxidation. Many people have latched on to this fact and started to claim that FASTED TRAINING RESULTS IN MORE FAT LOSS.
They have WRONGLY linked increased fat oxidation to fat loss.
We know that from a body composition stand point there are many factors that impact this, the main one being energy balance! And if you don’t believe me, believe Dr Brad Schoenfeld and Alan Aragon. They found no difference in body composition between fasted training and just training interventions.
It is the overall daily intake that is the most important thing for recovery and fat loss / muscle gain.
Nutrient timing isn't the be and end-all.
This is why there is so much debate on fasted training. It doesn't really matter if the rest of your diet is terrible. It can be of benefit if you do the right type of intensity and have your diet on point.
But what if I do high intensity exercise fasted?
So we’ve looked at the benefits of fasted training on endurance work, but a lot of people will likely carry out high-intensity training or resistance training early in the morning without eating simply because it fits in well with their lifestyle.
For high-intensity sessions similar to most Crossfit classes, the dominant energy system is likely to be anaerobic glycolysis, the substrate for this is CARBS!
The adaptations from these sessions will be slightly different to endurance sessions too so I’d highly recommend fuelling with carbs for these.
If you do not like eating in the morning before training, it could be worth looking at liquid calories and potentially even some intra-workout nutrition in the form of maltodextrin or something similar.
You’ll likely get more out of the session because we are aligning nutrition to the training.
Ok but what about strength and resistance training?
The adaptations here are again different from those seen in endurance exercise so fasting won’t necessarily bring about any extra gains BUT it may not inhibit them either. A recent study by Naharudin et al (2020) showed that resistance training performance was not impacted by low carb availability when subjects consumed a placebo meal tasting similar to that of a high carb meal. This is CRAZY!
The takeaway here is ultimately that if you’re used to resistance training when fasted, and you are not hungry during sessions, your performance should still be fine.
Common Faults When Training Fasted
There are several common faults with regards to training fasted in this way though let’s attack some of these now:
Doing fasted training sessions at too high an intensity! The training stimulus does not MATCH the nutrition protocol and so the adaptations won’t be amplified! Training fasted at high intensity is completely fine to do, it is just not optimal. And if you train too much and don't match your overall intake to your output, you run the risk of not progressing, feeling run down and burnt out.
Thinking you are fasted and in a state of low carb availability when you are not. It’s hard to directly measure this and many people fall into the trap of having something small that takes them out of the fasted state before hand!
Doing fasted sessions that last too long. Many people might underestimate the energy cost of exercise and try to take on too long of a fasted session.
Tips For Fasted Training
Plan your sessions accordingly to ensure you don’t fall into these traps.
Use a HR monitor to track intensity, keep your HR low, ideally Zone 1 or 2 work or at Fat max if you have accurate measurements of that.
Have a go-to pre workout routines such as water, black coffee or another carb free caffeine source. You could even go for a BCAA drink, this is one of the very rare occasions where I’d recommend it to slow down the rate of muscle protein breakdown while still remaining in the fasted state.
Let’s Finish With Some Key Takeaways
If the only time you can train is first thing in the morning and you are doing more endurance based training, DEFINITELY work some fasted training into your weekly plan.
If you do CrossFit or HIIT then it is totally cool to train fasted but maybe trial eating something beforehand on more strength-based sessions or harder workouts.
If you’re just wanting to get fitter, incorporating one or two fasted LOW INTENSITY sessions into the week could be beneficial.
If training for a specific comp or race, periodise your nutrition and incorporate more fasted sessions the further away from the race.
“Ensure you are eating enough overall and don’t let the nuances of fasted training stress you out. Overall intake is the most important factor.
If you are wanting to get stronger and train muscle then you’re probably not doing yourself a disservice if training fasted. Just eat enough!
Fasted training is great....but it is the magic bullet...JUST TRAIN!
If you’ve hit a plateau but train fasted, definitely look at increasing meal frequency and a pre training feed / drink is the perfect time to do that!”
