This is one of the most common questions you will hear about the optimal training session. Usually, proponents of fasted training will advise you to work out right after you have woken up and before breakfast. 

 

The most popular argument for this way of training is usually that it will burn more fat than normal if you eat before exercise because your body cannot use the energy from food to fuel your workout so it has to burn fat directly.

 

A common counterargument to this is that fat loss is not guaranteed because your body could just as well burn muscle tissue for energy and not eating before a workout will leave you hungry, therefore leading to decrease performance and fewer results overall.

 

As you can see, the debate about training fasted or not is a difficult one and you might easily get confused. That’s why today I want to look not at the theory but the actual research that was done to see which argument is backed by science.

 

We will look at the results from different studies on fasted training vs fed training in relation to four important factors:

 

– Appetite reduction

– Exercise performance

– Changes in weight, so the actual weight loss results

– And lastly changes in muscle mass

 

Let’s get started…

 

 

Appetite Reduction 

 

One good thing that studies have shown is that when training for fat loss, exercise is generally linked to less food intake. This means most people, whether they train fasted or fed will be less hungry and have fewer cravings if they exercise. We don’t exactly know why yet but it might be due to a change in brain receptors leading to less responsiveness.

 

When we look at the difference between fasted and fed training in appetite reduction, we can see that fed exercise reduced appetite to a greater extent than fasted exercise right after the workout session. However, this is not an argument against fasted training because when scientists measured the whole-day food intake and not just the food intake after the workout, they found no significant differences.

 

This means that even though exercise has a significant effect on appetite, research has not found any significant differences between fasted and fed training in the morning when food consumption is measured for the entire day.

 

 

 

When we look at fasted versus fed training in relation to workout performance interestingly enough researchers also found no significant difference in performance when they tested joggers running on a treadmill.

 

This somewhat goes against my personal experience and that of many people, where your workouts are a lot more challenging and difficult if you haven’t eaten before. 

 

So why is it that researchers found no difference?

 

What we have to keep in mind is that the study tested only jogging, which is only a mildly intense form of exercise. When we look at more intense workout programs like resistance training or HIIT, fasted training does, in fact, underperform compared to fed training as the lack of carbohydrates leads to less strength and explosiveness.

 

For me personally, this is actually the most important reason why I don’t train fasted. I simply feel too weak when I hit the gym without having eaten anything before. But if you are a fan of fasted training or want to minimize this negative effect, try taking a caffeine supplement before your workouts.

 

Caffeine can decrease the fatigue that comes with fasted training and will give you a short-term energy boost that enhances workouts.

 

 

 

On to the most important question:

 

Does fasted training actually burn more fat than fed training?

 

I know many people are convinced it does but does the data support this claim? Well, there is some evidence that fasted training leads to a greater percentage of energy coming from fatty acids rather than carbohydrates.

 

While this might be a good sign, what we are actually interested are any differences in overall fat loss and this is where the data is not so conclusive. There are both studies that have found a difference in fat loss over a period of time when comparing fasted vs fed training and studies that have found no significant differences.

 

What does that mean for you as the average trainee?

 

Should you train fasted or not?

 

Since the data is inconclusive and none of the differences in fat loss that were found in a few studies are extremely large I recommend you stick to what you like best. If, like me, you prefer to train fed than continue doing so.

 

If however, you like doing your workouts on an empty stomach you can also do that. In this case, you should consider supplementing with caffeine though as it will help with the fatigue.

 

Now, the last thing I want to talk about is the impact of fasted training on lean muscle mass. Unfortunately, there is another drawback to fasted training, especially when doing fasted weight training. It enhances muscle breakdown which we don’t want. Enhanced muscle breakdown means less lean muscle mass and fewer muscle gains after the workout.

 

So to avoid the increased breakdown of muscle tissue during fasted training, bodybuilders usually supplement with branched chain amino acids or BCAAs. These are three amino acids with similar structures that aid in muscle growth and maintenance. Since they are found in most forms of protein you usually don’t need to supplement them, but when training on an empty stomach it makes sense to take BCAA.

 

The bottom line on fasted vs fed training is actually a lot simpler than many people would think. Simply do what you prefer. If you, like many people, you need the extra energy before a workout feel free to eat a proper pre-workout meal. I explain how to this in my nutrition course.

 

If, however, you want to train fasted you can absolutely do this but I would advise supplementing with caffeine and BCAAs for better performance and less muscle breakdown. 

 

If they exist, changes in fat loss will be minimal between fed and fasted training so don’t obsess over details here. Instead, find a workout that is right for you and your lifestyle.