Working Out While Intermittent Fasting: Should You Be Doing It?

There have been many health and wellness fads and trends that have come and gone. People are always searching for that miraculous fix that will instantly reward them with their fitness goals. Truth be told, no such thing exists, and you’ll have to rely on working out and eating a clean diet.

So, what is intermittent fasting, and why is it so popular these days? And should you be working out while fasting? Here’s what we know.

What is intermittent fasting?

Intermittent fasting (IF) is an eating schedule that cycles between eating time and fasting time. It doesn’t specify what you should be eating, but when. By definition, IF is not a diet but more like an eating pattern or schedule.

The Science Behind Intermittent Fasting

The primary factor or hormone behind IF is insulin. When we eat food like carbs, our body converts them to glucose, which we use for energy. If we do not use that energy, they’re stored in the fat cells and become fat. They enter the fat cells through the hormone insulin, which brings glucose into the fat cells and keeps them there. If we do not eat for long periods, our insulin levels naturally go down, releasing the glucose from our fat cells. 

What happens when you work out while you’re fasting?

When you go 10-16 hours without eating, your body will go to your fat stores for energy, and fatty acids called ketones will enter your bloodstream, which has been shown to have incredible benefits for brain health.

When you work out fasted, you essentially burn more fats. This is because the carbohydrates stored in our bodies, called glycogen, are all but used up, so our bodies burn fat to fuel workouts. However, some studies refute this claim, indicating that fat burning remains the same.

Insulin sensitivity and maximizing growth hormones could be other benefits when working out while fasting. Insulin sensitivity refers to our cell’s responsiveness to insulin. High sensitivity to insulin allows your body to process it effectively, lowering your blood sugar levels. A 2018 literature review revealed a positive relationship between physical exercise and increased insulin sensitivity.

Should you work out while fasting?

As with everything in life, you should take this with a grain of salt. When answering this question, you have to think about what your fitness goals are.

If you want gains, you shouldn’t work out while fasting.

One of the great benefits of intermittent fasting is calorie control. You’re expected to experience a caloric deficit when intermittent fasting because of its entire structure. Because IF limits the time you have to eat, most people won’t get to consume the same amount of calories they usually would.

A caloric deficit is counterintuitive to your muscle-building goals. It’s a general practice that when trying to gain muscle, you’ll need to have a caloric surplus, not a deficit. Your fitness goals should be fat loss, not muscle growth, if you want to work out while fasting. However, if you’re going to build muscle while maintaining an IF schedule, you should ensure that you meet your caloric requirements.

You should note that while working out and fasting will not result in the most considerable muscle growth, you should still lift. Even if fat loss is your goal, you should lift to avoid losing muscle mass. Lifting will prevent muscle loss, preventing your body from burning through muscles for energy.

For more strenuous workouts like HIIT, Crossfit WODs, heavy lifting, and other high-intensity workouts, you should eat before you lift. These workouts rely heavily on carbohydrates for energy, so it’s recommended to grab a quick bite before starting. If you’re aiming for peak performance, you won’t want to work out during your fasting window.