Intermittent fasting can be an excellent tool for weight loss and an effective way to stick to a diet when you’re training.
But if you are doing intermittent fasting while you have a full-time job and a family, it can be difficult to schedule your fasting window for a convenient time.
Can you go running on an empty stomach before you break your fast? Are there any negative effects that can happen when you train fasted?
Let’s have a look at the advantages and disadvantages of running on an empty stomach.
Should you go running on an empty stomach?
When you go running after you’ve eaten, your body uses those nutrients to fuel itself through your exercise. But when you go running on an empty stomach, your body has no carbohydrates to access for fuel. So it begins to burn your body fat as fuel.
But fat doesn’t fuel the body the same way as carbohydrates do. You may run out of energy sooner and there’s also a chance of muscle breaking down as your body may start breaking down protein for fuel as well.
It is recommended not to run on an empty stomach. If you do choose to run in a fasted state, pay attention to your body and rest if you start to feel weak or lightheaded. You may also want to take an energy bar or energy gel with you so that you can fuel up if you start to feel lightheaded.
Individuals with diabetes or metabolic disorders should not run on an empty stomach. It may also be best to eat before running long distances or doing high-intensity exercise.
What happens when you don’t eat?
When you eat, the glycogen levels in your muscles are replenished. Glycogen is how carbohydrates are stored. When you don’t eat, your glycogen levels drop. The longer you fast, the more your glycogen levels are reduced.
When you exercise, your body relies on carbohydrates for energy. When you don’t eat before running, your body has to rely on glycogen. But when you haven’t eaten for many hours, the glycogen stores in your muscle are not enough to push you through your workout. That’s why your body begins to burn more fat.
Although this can be beneficial for fat loss, it can also make your workout less effective as you will most likely run out of energy before you would if you had eaten.
Are there benefits to running on an empty stomach?
Running on an empty stomach isn’t all bad. A reduced energy intake means you can burn more fat than training on a full stomach. Individuals who are prone to sensitive stomachs may also benefit from running without eating first.
Some individuals may enjoy running on an empty stomach as they don’t feel too full or weighed down. For some, a small, simple meal like an energy bar may be enough to fuel them through a run. But others may feel that any food makes them feel sluggish and uncomfortable.
It is important to note that depending on what your last meal was, you may only be completely fasted 8 to 12 hours after the meal. For example, if you run 6 hours after a meal, you may feel like your stomach is empty, but your glycogen levels may still be elevated.
Generally, you will be completely fasted after a night of sleep. It takes only about 30 calories to break a fast, which counts as your stomach not being empty.
That means if you are drinking coffee with cream and sugar before you’re going for a run in the morning, you won’t be running on an empty stomach anymore.
Disadvantages of running on an empty stomach
Depending on what your running goals are, running on an empty stomach may have more disadvantages than advantages.
If endurance is your goal, running without eating first may reduce your performance. You could feel tired much sooner than you normally would on your run, or find your muscles fatiguing long before they would if you worked out after a meal.
If fat burning is your goal, exercising without eating may help but there is a chance of losing muscle mass. Individuals who wish to do strength training to build muscle should not exercise on an empty stomach unless taking branched-chain amino acids to preserve muscle.
Running on an empty stomach may also lead to overeating later on. You will need to fuel your body after eating, but hunger may lead to eating more than you need.
Make sure to eat nutrient-dense foods and include protein and healthy carbs—fruits, vegetables, rice, pasta, etc—at every meal. This will fill you up quicker and keep you full for longer.
If want to run on an empty stomach
Some individuals may feel better when running on an empty stomach, especially runners who have sensitive stomachs. If you want to run on an empty stomach but still perform well, you can do so with a bit of planning.
Having a high-carbohydrate meal the evening before—if you run in the morning—or on the morning of your run—if you run in the evening—can elevate your glycogen levels enough to see you through your run. Be sure to include protein in your meal too. Pasta and meat or rice and meat are both good options.
Run for between 40 and 60 minutes. Any longer than that and you will probably need an energy bar to replenish your carbs and give you enough energy to continue. Low to medium intensity is the best pace so that you don’t overexert yourself.
Make sure to stay well-hydrated throughout your run and keep your electrolyte levels up. You can use electrolyte tablets, sports drink sachets or even energy gels or chews. But if you don’t want to break your fast, make sure you stick to sports drinks, electrolyte tablets or energy gels that contain less than 30 calories.
To avoid losing muscle mass while running on an empty stomach, you can take a BCAA (branched-chain amino acid) supplement. You can sometimes find energy gels or sports drinks that contain BCAAs.
Always hydrate before a morning run
If you are fasting during the day and running in the evening, you will most likely be drinking throughout the day. But it’s more common to fast overnight and run in the morning on an empty stomach.
If this is your schedule, you will need to hydrate before you run. If you haven’t had anything to drink the whole night, you will be dehydrated even if you don’t feel it.
Drink at least one 8-ounce glass of water when you get up to rehydrate yourself before doing any form of exercise. Make sure you don’t drink it right before you run, as you might find yourself needing to stop for a bathroom break during your run.
The first 30 minutes to an hour after your run is known as the anabolic window. Your body can absorb nutrients more effectively during this time, so it’s important to have a good post-workout meal to replenish your glycogen stores and nutrients.
Remember, your post-workout meal should be balanced. Choose healthy carbs to replenish your glycogen stores. Protein should be present too, to help repair muscle. Also, remember to keep hydrating even after your run.