Should I Run on an Empty Stomach?

Whether or not you should be running on an empty stomach is a topic that brings about much debate and varying opinions.

There are individuals who absolutely swear by their fasted training regime and then there are those that are wholeheartedly against it.

So, which side is correct?

Or is it simply a matter of personal preference?

This article will examine the main reasons for people to use fasted training and decipher whether or not it actually has any merit. Once you understand each side of the story, you can make the decision to which option might suit your training needs the best.

There are generally two theoretical reasons for people to run on an empty stomach. The first is for fat loss and the second reason is for increased performance.

Fasted Running for Fat Loss

The idea here is that running before eating anything has the ability to force your body to burn fat for fuel instead of your glucose stores.

When you exercise, your body has two main sources of energy: glucose and fatty acids. Depending on the level of intensity and what is available inside your body, you will use varying amounts of each energy source.

The glucose in your blood and that stored in your muscles and liver, which is obtained from eating carbohydrates, will usually be your body’s preferred energy source as it is more readily available.

However, if you haven’t eaten, there will be less glucose available in the bloodstream and any exercise you do will be fuelled by fatty acids instead. That is the theory anyway.

While this theory can work out, if done correctly, it still doesn’t necessarily lead to fat loss.

The biggest factor in fat burning comes down to overall energy balance. If you are eating more calories than you burn, you gain weight and if you are burning more than you eat, you lose it.

That is really as simple as it gets for weight loss. It doesn’t really matter if your running is fasted or not. What matters is your total calorie intake compared to your calorie burn.

You could argue that not eating before running helps you eat fewer calories throughout the day, which could be true for some. On the other hand, training fasted causes great hunger levels for other people and can lead to overeating after your running session. Everybody responds differently.

In terms of fasted training directly helping with fat loss, science suggests that it doesn’t. A study in 2014 was done by the journal of the international society of sports nutrition to examine this exact theory.

The study compared a group of people who performed aerobic exercise after a meal to a group that had fasted overnight before the exercise session. After a month, no significant differences were found in terms of body composition between the groups.

The good news is, whether fasted or not, your body will thank you for your commitment to being physically active.

There is a greater chance of increased training time with your own exercise equipment. If you are looking for a treadmill to help you achieve the benefits of running, you can check out our review of the best affordable treadmills in this post.

Running on an Empty Stomach for Performance

There are some individuals that believe running on an empty stomach can have some performance benefits, specifically for endurance.

The theory is that the fatty acids used by your body when fasted provide a longer lasting energy solution that is more geared for endurance based exercise.

This is all well and good, your body can sustain bouts of activity without the need for glucose for hours. The trouble is that the activity has to be of low intensity.

If you want to push the intensity up, you really will need some glucose to fuel your efforts. Obviously, for performance, you are going to want to be pushing the intensity up at some point or another if you want to improve your times.

Therefore, it would make sense for you to make sure you have the glucose available to do so. Running on an empty stomach just cannot guarantee that you will indeed have enough in the tank for higher intensities.

On top of the physical need for fuel, there has actually been some interesting research into the psychological effects of believing that your body is fuelled for activity.

There was a 2014 study that gave one group of exercisers water and another group a flavorless carbohydrate drink. Both groups rinsed the liquid around their mouths but spat it out instead of ingesting it.

There were significant performance increases in the carbohydrate solution group even though no energy could have been gained from just rinsing their mouths with the liquid.

The given explanation is that your brain receives signals from your mouth that indicate food/energy is being ingested. The body’s response is to make more energy readily available, which is another reason why performance is likely to be better after eating.

Final Thoughts and Recommendations

After reading the points made above, you are probably thinking that it seems pretty cut and dry. It definitely appears that running on an empty stomach has no positive effects on neither fat loss or performance.

However, personal anecdote should not be discounted. There are numerous people that really do run better on an empty stomach.

Whether it’s down to them being genetically better prepared to cope with fasted training or because they just don’t like to feel food in their stomach at all when they run, some runners simply prefer to run on an empty stomach.

All you can really do is test it out for yourself and see how your own body responds. If you do try it, give yourself at least a couple of weeks for your body to actually adapt to the fasted training before you decide whether you like it or not.

After two weeks, you can decide whether to continue fasted training or not depending on how you are feeling and performing.

If your performance drops or you feel terrible, forget running on an empty stomach.

If you run faster and feel good then training fasted clearly agrees with you so you can carry on.

Finally, if you see no real difference then you can decide purely on what suits your lifestyle and feels best to you.

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