Fasted vs non-fasted running

Breakfast before morning run or just after? Some of the runners like to eat something before hitting the road, at the same time others struggle with breakfast. Early morning run, often means even earlier breakfast. It is suitable to eat breakfast at least an hour before the run, which might mean very early wake-up.

The general rule can be, if you are going to run over one hour, eat breakfast. Shorter runs can be done in fasted, but if you need something after the night, but don’t want wake-up early eat a banana or something small.

Fasted running

Fasted running means that you are going to running without breakfast. It takes 10-14 hour to get fully fasted state, but in the morning your glycogen storages are already slightly depleted. This means your body needs to find alternative energy, which means fat sources. Many people automatically think this will burn fat and help with weight loss. Which is partly true. Although, the body doesn’t only use fat sources during the fasted state, and the best results for fasted state and weight loss combination would be high-intensity training, like intervals. A calorie is always a calorie, whether is from fat or carbohydrate. The only way to lose weight is to get calorie depleted.

On the hand, doing the high-intensity training in a fasted state might cause fatigue and fainting for some people. It can also decrease the performance, as there is no quick fuel available.

non-fasted running

Eating breakfast before the morning run is good if the exercise will be longer than an hour or you need energy. Breakfast also helps post-run recovery. Studies have also shown that non-fasting runners perform well better aerobically in the longer run.

Breakfast can cause stomach problems, especially if it’s enjoyed too near for the exercise. Take at least one hour break after breakfast, or eat something light.

take home message

  1. Don’t do any high interval training in fasted.
  2. Intensity should max 65% if fasted.
  3. No longer than 60 min exercises if fasted.
  4. Fasted improve insulin sensitivity.
  5. Eat light or eat at least one hour before running, if non-fasted.

Terada, T., Eshghi, S. R. T., Liubaoerjijin, Y., Kennedy, M., Myette-Côté, E., Fletcher, K., & Boulé, N. G. (2019). Overnight fasting compromises exercise intensity and volume during sprint interval training but improves high-intensity aerobic endurance. The Journal of sports medicine and physical fitness59(3), 357-365.

2 thoughts on “Fasted vs non-fasted running

  1. Hi! I usually run before breakfast, and I have a question: why running max 60 minutes when faster? Thanks.

    1. Hi! Muscle glycogen levels are low in the morning, and when you are running, you need glycogen, so prolonged running, might lead glycogen depletion, which causes a decrease in strength and performance. Also, recovery suffers and in the worst-case scenario, high intensity and long exercise without energy might cause nausea, fatigue and fainting. So, if you go longer run, it might be a good idea to take some energy, like gels or sports drinks.

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