Combining fasting and working out can help burn unwanted fat faster than either fasting alone or exercise by itself. You can even gain muscle if you pair fasting with exercising carefully.

In this article, we’ll look at how intermittent fasting and working out can help you reach your fitness goals safely. I’ll also answer a few of the most frequently asked questions around the subject to help you get the best results out of your fast.

Intermittent Fasting and Exercise Timing

If you’re someone who works out regularly but wants to try fasting as well, there are some things you should know beforehand. Research shows that exercising while you’re fasting can affect metabolism and biochemistry linked to steady control of blood sugar levels and insulin sensitivity. 

There have been many studies done to show the different results between working out in a fast state vs a fed state. In one study it was shown that people who had a fasted exercise session had improved results when it came to their muscle’s ability to burn fat during exercise, as well as the body’s ability to keep up its blood sugar levels, unlike the people who had a fed exercise. 

Intermittent fasting and working out in the morning can have added benefits. Since you’re near the end of your fast, your body is no longer storing fat but is burning it instead. By working out in the morning you burn more of the fat your body has been storing. 

Fasted Workouts – Frequently Asked Questions

Most people have plenty of questions about working out and fasting and, if you’re here, chances are you are one of those people. I answer some of the most commonly asked questions below.

Is working out while fasting safe?

There can be some dangers of working out on an empty stomach, especially when you’re new to fasting and your body is still adjusting to the schedule. You may feel like you have less energy to devote to your workout on an empty stomach, making it hard for you to give it your all. In some cases, you may get a little dizzy or feel light-headed.

In general, these side effects slowly fade as your body becomes more used to fasting, and there is even research that shows exercise in a fasted state, if you’re otherwise healthy and well-nourished, can protect your muscles and build them faster.

Does working out while fasting burn more fat?

You may be wondering, does working out on an empty stomach burn more fat? Yes, you will burn more fat in a fasted state as opposed to a fed state because your body has fat stored in your muscle tissue. When you work out fasted, your body will burn this fat first and then move on to other nutrient sources, like from your adipose tissue, and put the energy towards building your muscle mass. Eating after a fasted workout has been shown to be 3x as effective at burning fat as eating before a workout.

Does working out white fasting burn more fat?

Can you build muscle while fasting?

There are few reliable studies that talk about building muscle while fasting.

One experiment placed 18 young men on an 8-week fasted resistance training program. None of these men had previously focused on weight training. A percentage stayed on their normal diets while the others started only eating in a 4-hour window, 4 days a week. At the end of the experiment, the men who hadn’t changed their diets gained 5lbs of lean mass and increased their strength. The men who had a restriction to when they could eat had maintained their lean body mass while also increasing their strength.

This test had one major flaw, however: what food and how much was eaten in each group was not monitored. If the control group was eating more protein on average than the study group, this could drastically alter the results. 

The most scientific schools of thought believe that fasting, especially in addition to a well balanced and highly nutritious regular diet, better prepares your body to burn fat for fuel, which is actually muscle sparing. If you work out in a fasted state, this encourages your body to burn more fat and use the excess energy triggered by your natural stress response to build muscle instead. So yes, you absolutely can build muscle while fasting.

Moreover, studies have shown that post-workout meals are as much as 2x more effective for muscle building when compared to working out in a fed state. This is due to protein synthesis. 

Protein is the foundation of every single cell in our bodies and it also helps our cells function. Protein synthesis is the process of creating the protein to build our bodies.

Should I do cardio while intermittent fasting?

Small studies have shown that fasted cardio might burn up to 20% more fat compared to when you work out with food in your belly. Your body uses stored nutrients to gain energy, which results in burning them off. 

High-intensity interval training (HIIT) while fasting can be the best and most efficient way to lose fat, and still retain muscle mass. Fasted sprints can be one of the best ways to lose unwanted fat due to the spike in the growth hormone and the decrease in insulin. Try doing the sprints last so you won’t be too tired to do your regular workout. 

One of the best ways to do HIIT sprints is by jumping on a treadmill and setting two speeds, a sprint speed, and a more relaxed jogging speed. By doing this you’ll jog for 1 – 2 minutes and then sprint all-out for 20 seconds, with as many intervals as you can for a maximum of half an hour. Practicing Intense work out like HIIT while fasting means you are already confirmed in the fasting method.

Intermittent fasting and exercise results – what can I expect?

Intermittent fasting and exercise each affect people in unique and individual ways; put them together and results are going to be very different for every single person. Usually, the results will be positively surprising!

One woman was shocked by her first experience pairing exercise with intermittent fasting for weight loss. At first, she couldn’t stop thinking about food however, as the days went on, it became easier and easier. This is common for all new diets or habits. 

Her results after 1 week included significantly less bloating and improved focus. By the end of 1 month, she realized she had become much more self-aware of her eating habits, cutting down on boredom snacking, and snacking on unhealthy things like chips, or cookies. This alone is a fantastic recipe for weight loss and overall better health!

Is Fasting and Working Out For You?

Fasting and working out can be a great way to burn fat and build muscle, but make sure you’re always listening to your body. If you ever start to feel dizzy or weak, you may be dehydrated or you have low blood sugar. Always work out and fast responsibly and with the approval of your doctor, especially if you have any prior health conditions.

If you’re looking for more ways fasting can make weight loss sustainable in your life, check out our post, Fasting To Lose Weight, to see if it would be a good fit for you.


Case Studies and Research