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Running on an Empty Stomach

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It’s a debate that has plagued the running world for many many years: Is it better or worse to run on an empty stomach?

The truth of the matter is, there is no right or wrong answer. Different runners run best under different circumstances. Making a blanket statement on whether a runner should eat before running is like telling all runners what time of day is best to run or what brand of shoe will work best for them. All of these things, including whether a runner should run on an empty stomach, largely depends on what works best for the runner.

Whether or not a runner decides to run on an empty stomach is solely up to their own discretion. However, there are a few things to consider.

Hydrate, Hydrate, Hydrate.

For runs, especially longer ones, all runners want to be properly hydrated.  Runners need to take in more water than the average person to cover their sweat losses. During a high-intensity workout like running, a person could lose approximately 18-35 fl oz per hour. Drink before, during, and after your run to prevent dehydration.

Fuel Up Before a Longer Run

If your planning on running for more than 1 hour, it’s best eat at least a small meal. Long and more intense runs require more energy. If you push through a long run without eating, you’re putting your body at risk for fatigue, dizziness, hunger pains, cramping, and/or the potential to pass out.

The Science Behind Fasted Running

Your body does not want to burn its fat reserves. Instead, your body wants to use what is easily accessible. After fasting for eight to 12 hours (like overnight sleeping), your body will automatically begin burning the carbs stored in your muscles and liver for energy. Once your body runs out of carbs, stored fat will begin to burn. However, stored fat takes longer to convert into energy.

If you’re planning on a light to moderate run for less than 90 minutes, your body should be able to turn fat into energy without you having to eat ahead of time.  However, the body can’t mobilize fat stores while burning enough to sustain energy during high intensive runs. This means once the body runs out of carbohydrates, it will no longer be able to continue working at that intensity. What does that mean for you? If you’re planning on a long or intense run, your performance will suffer from fasting beforehand.

Cons to Running on an Empty Stomach

Along with burning fat during your run, your body also burns fat after a run. This is known as excess post-exercise oxygen consumption. If you end a run feeling washed out, you increase your body’s risk of overeating later in the day. Fasting before workouts also puts added stress on your body. Stress causes the release of cortisol. This means your body will break down muscle to use protein as fuel.

Benefits to Running on an Empty Stomach

A benefit to fasted workouts is improvement in muscle glycogen storage efficiency. This means that running on an empty stomach can help the body learn to better use its energy stores. Occasionally running on an empty stomach can improve the quality of regular runs later on. When the body learns to perform without food, it becomes more efficient performing when it does have a food source stored.

Here are a few more tips and helpful information to keep in mind if you do choose to run on an empty stomach:

  • It’s true that fasted running will take your body some time to get used to. Your body has been programmed to expect body before any activity. The initial discomfort will pass.
  • Have more than just water. Feel free to have plain tea, black coffee, or any supplement that’s calorie-free (or very close to it).
  • Bring along a sports drink and/or a snack in case you need it during your run
  • Break your fast whenever you’d like.
  • Eat as many meals as you’d like throughout the day (Not as many calories as you’d like).
  • If fasting just isn’t for you, then there’s no need to keep it up. Just don’t be afraid to try it out for a few runs and see if it’s beneficial to you.
  • And remember, if you have a condition such as diabetes, make sure to discuss this with your doctor prior to beginning a running schedule that includes fasting.

The ideal time to eat before running is at least 90 minutes to 2 hours before. This gives the body enough time to digest your food and allows you to still be fueled for your run. If you’re running for under an hour at low intensity, your body doesn’t require the extra digestion and fuel so, feel free to eat or not eat.

If you have been running on an empty stomach and haven’t had any negative effects such as being light-headed, dizzy, overly fatigued, or low on energy, you can continue your fasted runs. However, as a precaution, you should always bring along an energy bar or sports drink in case you suddenly find yourself worn out or dizzy.

There is no right or wrong answer when it comes to running on an empty stomach. If you want to try fasted running, give it a shot. As a runner, you know if something is or isn’t working in your best interest. If running on an empty stomach works for you, great! If running on an empty stomach doesn’t work for you, great! The most important thing to remember is to always listen to your body.