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What Is Fasted Cardio and Why Should You Consider It?

Working out while fasting might seem like hungry, hard work, but it could be a way to maximize that fat burn. Celebrities like power couple Jennifer Lopez and Alex Rodriguez swear by pre-breakfast workouts, and many personal trainers also recommend the practice. But what is fasted cardio, and how can it help you burn calories?

What Is Fasted Cardio?

Working out fasted or a fasted workout literally means doing your gym session or cardio on an empty stomach. What is fasting? Fasting is any period of time when you don’t eat any food and drink only water. This means that your body is not taking in energy from food. In theory, exercising four to six hours after eating should encourage your body to burn stored fat for energy, so the pounds should melt away.

Is cardio good for weight loss anyway? Yes, absolutely. Cardio is thought to burn more calories per session than lifting weights, although it may not help you build muscle mass as fast. So why do fasted cardio? It’s thought that exercising on an empty stomach could be the key to faster weight loss and minimizing body fat via an understanding of the way our bodies deal with energy usage.

The Best Time to Do Fasted Cardio

Best Time to Do Fasted Cardio

For many people, doing fasted cardio in the morning is the simplest way to achieve a fasted cardio session. This is because you’ve already fasted all night, so all you have to do is make sure you get your morning cardio session before you eat your breakfast.

Fasted sprints, fasted aerobics, even fasted swimming can all be easy ways to kick start your day and burn some major calories.

Benefits of Fasted Cardio

We all know the top cardio benefits: improved cardiovascular system. But what are the benefits of doing cardio in a fasted state?

  • Potential for greater weight loss
  • Increased lipolysis
  • Increased fat oxidation
  • Lower insulin levels

Weight Loss

Both the processes of lipolysis and fat oxidation break down fatty cells and burn them as fuel for movement. This means that when you exercise on an empty stomach, you are burning your fat reserves, which should reduce your overall body fat.

What About Intermittent Fasting?

Intermittent fasting is a popular diet trend linked to weight loss. The idea is that you have fasting days and non-fasting days. Fasting days are calorie limited, and you might not eat at all for many hours. On fasting days, you might only eat 500 calories, and nutritionists recommend these calories are taken in via healthy foods like vegetables and filling proteins like pulses.

Intermittent fasting fits right in with fasted cardio because those on this type of diet can easily slot in a fasted cardio session during one of their periods of fasting. Eating to a schedule like this means you can plan your workouts around it, and ensure you are always exercising on an empty stomach. 

Just make sure you’re eating enough healthy food during your non-fasting times to fuel your hard-working muscles, heart, and lungs. Running on empty isn’t good for anyone, and you can wear your body out if you don’t “top up” with the right kinds of foods regularly.

Is Fasted Cardio Safe?

It’s normal to worry that fasting and working out might be detrimental to your health. Some nutritionists don’t recommend fasting at all, stating that it can cause food “rebounds” and cravings. However, if you’re exercising before a healthy breakfast, this shouldn’t be an issue as your nighttime fast is completely natural.

It’s normal for blood sugar levels to be lower when you have fasted. Exercising may lower these further, which may lead to you feeling light-headed and tired. This is normal, however, if these symptoms become uncomfortable or cause concern, speak to a medical professional. Those with diabetes should consult a doctor before doing any fasting.

Another side effect of fasting cardio is potential muscle loss, especially in those that don’t have much body fat to burn. This is simply because your body has to get the energy to exercise from somewhere. If there’s no food and no fat, the muscle starts to get repurposed as fuel.

Those in good health with no long-term medical issues should be able to do fasted cardio without any concerns at all. If weight loss is your goal, fasted cardio could help you lose up to 20% more fat than exercising with a full stomach, so it’s definitely worth a try.

What to Eat After Fasted Cardio?

What to Eat After Fasted Cardio

Whether you’re already working your cardio in and around your intermittent fasting, or you’ve just done fasting cardio for the first time, you need to make sure you’re getting plenty of healthy food after exercise. The right foods stop you from feeling lethargic and can help you rebuild muscle. Here are some ideas on what to eat after fasting and working out:

  • Protein shakes to help rebuild muscle- add coconut oil to combat muscle loss
  • At least 8oz water (avoid sugary drinks)
  • Bananas
  • Plain yogurt
  • Berries
  • Tuna or salmon
  • Eggs
  • Wholegrain cereal with milk
  • Avocado on wholegrain toast
  • Oatmeal

With foods like these, you’re replenishing your body’s energy levels, giving it the protein it needs to build or repair muscle, but not restocking all the fat you just burnt. Skipping a meal after cardio does not have the same benefits as training on an empty stomach, and could leave you feeling very tired or ill.

If you want to try fasted cardio, see how your body copes with just a little fuel, like some toast or yogurt. If you can exercise fine after minimal food, try exercising on an empty stomach. You might find that it feels more energizing, and you may even see better weight loss results.


Fasted cardio means doing cardiovascular exercise on an empty stomach. Training four to six hours after eating may burn more fat than training on a full stomach. The easiest time to do fasted cardio is on a morning before breakfast.

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