Running on an empty stomach means running in the morning before having breakfast. Most of the time, it means heading out for a run shortly after waking up, about ten hours after your last meal, dinner. Some people do it for practical reasons, because it is the only way for them to fit a run into the day before going to work. Others do it for sporting or well-being reasons. What are the effects and benefits of running on an empty stomach? You will find more information on fasted running here.
The short answer
- Running on an empty stomach means running in the morning before breakfast, about 10 hours after dinner.
- Your body uses slightly more fat during the session, but studies do not show greater weight loss in the long term.
- Stay at an easy endurance pace, 30 to 50 minutes, and avoid intervals on an empty stomach.
- Drink before you go, carry a snack, and do not run fasted every day.
Contents
Running on an empty stomach in the morning: why do it?
Fasted runs usually take place shortly after waking up. They allow many runners to fit their run into a busy schedule, and to get energized for the day!
If you had to run in the morning and wait 2 hours to digest your breakfast, you would potentially have to get up very early! Except at the weekend, when you can have breakfast around 7:30-8 am and go running at 10 am.
Running on an empty stomach to burn fat
So what does running on an empty stomach change? In the morning, after about ten hours without food, the body normally has low blood sugar (little sugar available). It is mainly the liver’s sugar store (liver glycogen) that has dropped overnight; the muscles’ store remains largely available. During an easy fasted run, your body therefore uses a slightly larger share of fat.
When you wake up, the liver provides a limited source of sugar, called liver glycogen. This store runs out quickly during physical exercise. When you run on an empty stomach, fats or lipids (triglycerides or fatty acids) take over so you can keep running, while maintaining the body’s vital functions.
Getting used to running with low blood sugar
The more you train your body to tap into its fat reserves, the more you develop your endurance and your ability to cope with a drop in blood sugar. Useful for marathon runners who want to push back the famous wall at the 30th kilometer, and for trail runners! However, the real effect on performance is still debated. For a marathon, the best protection against the wall remains a sensible starting pace and taking in carbohydrates during the race.
Running on an empty stomach to lose weight?
Burning more fat during the session does not mean losing more weight. When researchers compare people doing the same training fasted or after eating, with the same diet, weight and fat loss are similar (Schoenfeld et al., 2014; Hackett and Hagstrom, 2017). To lose weight by running, what matters is your total energy expenditure and your diet over the week.
The weight loss you measure right after your run comes mainly from the water lost through sweat. For energy expenditure, count about 1 kcal per kilo per kilometer: a 70 kg person running 10 km burns around 700 kcal. To go further: what pace to run to lose weight.
Our practical tips for running on an empty stomach
- When you get up, drink some water or herbal tea.
- Wait 10 to 15 minutes to be fully awake.
- Warm up your ankles and joints and do 1 or 2 dynamic stretches.
- Run for 30 to 50 minutes.
- Run at an easy endurance pace (you should be able to talk during this run).
In any case, it is often harder to run fast in the morning. Avoid interval sessions or very intense cardio efforts. To wake up your muscles gently, you can also walk for the first 2 minutes.
Don’t run on an empty stomach every day, and take a snack if needed
It is recommended to run on an empty stomach no more than once every two days. Done too often, these runs can eat into your recovery and your form for key sessions, because running fasted can be tiring.
For your first fasted runs, take a little sugar, a cereal bar or a fruit pouch with you, so you have a source of carbohydrates in case your blood sugar drops too low.
Get to know yourself and be careful. The first few times, don’t go too far from home. And don’t go for a fasted run if you feel too tired.
If you have diabetes or take medication that affects your blood sugar, ask your doctor for advice before running on an empty stomach.
Breakfast after your run
When you get back, the ideal is to have a sports breakfast with protein and fruit, such as an egg and a banana. Eating within the hour after your run helps you recover well.
Running in the morning, before a day at work for example, is the perfect way to feel good and start the day with a smile.
Frequently asked questions about running on an empty stomach
How long should you run on an empty stomach?
30 to 50 minutes at an easy endurance pace is enough. For longer runs, take a snack with you.
Does running on an empty stomach make you lose weight faster?
No. You use slightly more fat during the session, but over several weeks weight loss is the same as after eating, with the same energy expenditure and diet.
Can you do intervals on an empty stomach?
It is better to avoid it: intense efforts mainly use sugar, and the quality of the session will suffer.
Should you drink before running on an empty stomach?
Yes. A large glass of water when you wake up makes up for part of the night without drinking.
Sources
- Schoenfeld B.J. et al. (2014). Body composition changes associated with fasted versus non-fasted aerobic exercise. JISSN, 11, 54. DOI: 10.1186/s12970-014-0054-7
- Hackett D., Hagstrom A.D. (2017). Effect of overnight fasted exercise on weight loss and body composition: a systematic review and meta-analysis. J. Funct. Morphol. Kinesiol., 2(4), 43. DOI: 10.3390/jfmk2040043
- Margaria R. et al. (1963). Energy cost of running. Journal of Applied Physiology, 18(2), 367-370. DOI: 10.1152/jappl.1963.18.2.367
