If you have recently got into the world of running or are a complete beginner, you may have heard people talking about whether you should run on a full stomach or an empty stomach.
There is some debate about this in the running community: is running on an empty stomach good or bad?
Some runners develop the habit of running on an empty stomach due to competition nerves. Others suggest it makes their performance better.
A scientific look at the subject, however, can reveal the truth. We can learn whether an empty stomach is BAD for our practice or if it can BOOST our performance. Or maybe both are positive.
We investigated so you don’t have to, see if you can improve your running performance by reading our article!
Fasted exercise refers to doing exercise, running or otherwise, while in a state of fasting.
When we are talking about running on an empty stomach we don’t just mean running when you are hungry or when you are on a diet. We are talking about running when your stomach is literally empty and in a cycle of fasting.
Often this is undertaken after around 6 to 8 hours of overnight fasting. You go for a run in the morning before eating breakfast. Water is all you need.
Proper hydration for a morning run is vital as running dehydrated can be harmful.
The fans of fasted exercise suggest that by not eating they have low glycogen levels. Glycogen is carbohydrates in the stored form in our body and is what your body will rely on for energy.
Those who undertake fasted exercise suggest these lower levels of glycogen can improve their performance.
Let’s explore this claim in more depth.
Can Fasted Running Burn More Fat?
One of the biggest things fasted running is popular for is purported fat burning.
It is suggested that as a result of low glycogen levels, your body will CONSUME your fat stores more readily, leading to a more effective fat loss.
It’s unclear from the scientific research if this is a placebo effect caused by hunger or if there is scientific evidence that this does occur.
While it makes theoretical sense that fasted exercise could lead to great fat loss, the research can be conflicting.
Some studies suggest that running before breakfast may allow you to lose more weight. But other studies state that it remains unclear whether training in the fasted state leads to more significant weight loss.
One study found that those who had a correctly balanced meal before running burned more than those who fasted before exercise.
The Healthline has a good discussion of fasted cardio’s pros and cons in its article. It came to a conclusion:
- Don’t exercise without eating for more than 60 minutes when trying fasted cardio.
- Choose low- to moderate-intensity workouts.
- Drinking water is part of fasted cardio, so stay hydrated.
- Lifestyle factors, such as nutrition, play a much more significant role in weight gain or loss than workout timing.
- You should listen to your body and do what feels right for you.
So, according to the research, there is no hard evidence to support the link between fasting and fat loss in an obvious way.
Weight loss likely occurs due to a calorie deficit, whether exercise is done on an empty stomach or not.
It’s clear more research is needed on this topic to really understand what’s going on.
Benefits Of Fasted Exercise
There can be scientifically reputable evidence that suggests there are some benefits to fasted exercise.
Reduced Nausea And Stomach Issues
Some people find that when they run they can get stomach cramps, digestion problems, and even diarrhea and vomiting in extreme situations.
If you train for long periods of time, such as a long-distance runner, then you will experience this often.
Running on an empty stomach can certainly help with this.
Some people, particularly those who run long distances, find that eating before they run can be a little pointless. They will end up wasting the energy they just consumed pretty quickly while it isn’t necessary to do so.
This is true, and in these cases consider using energy gels or other food supplements to give you the energy you need but without wasting good food.
Disadvantages Of Fasted Exercise
There are certainly disadvantages to fasted exercise.
Training Intensity Reduced
Sure, when you do fasted exercise your body will naturally go into your fat stores due to reduced glycogen levels.
However, this means that your intensity will be significantly reduced, which means that you won’t be able to run for longer.
Eat before you run and you can run for longer and further.
There is a large risk of injury when you don’t eat before running.
The more fatigued your body is and the harder it is for it to recall energy, the more likely it is for things to sprain, etc.
Your brain also needs glycogen levels to be normal for proper function so can actually be dangerous for trips and such.
High Cortisol And Muscle Loss
When you wake up your cortisol levels are at their highest.
Cortisol is a hormone that will contribute to muscle breakdown and weakness as a result of other functions this hormone controls.
Moreover, when you fast overnight, these cortisol levels will be even higher.
When you fast overnight and then go for a run in the morning, your cortisol levels are at their highest.
Therefore, running on an empty stomach in the morning can lead to more muscle loss and weakness in general.
Certain conditions mean fasted exercise can be a complete no zone. You can end up having low blood sugar levels when fasting. When this occurs, running can be very dangerous.
The Bottom Line
There is no one method that works for everyone. Not everyone wants to eat before a run, that’s totally fine.
- Consider doing a much lighter run or jog if you choose to fast before heading out.
- Consider eating something small or something like a food supplement drink before running to reduce nausea.
If you want to get the best performance and safety, you should probably at least have something in your stomach.