Can Exercising on a Empty Stomach Cause More Fat Burn?

What gets you to lose more fat?

A way besides changing your diet and working out more. One thing that has been spreading and raved in the fitness industry lately is working out on an empty stomach.

To find out exactly what this working out on an empty stomach is all about and how it boosts your fat burn, we reached out to an elite fitness expert, Ryan Chow, NASM-CES certified personal trainer at Focus Integrated Fitness NYC. 

Keep reading to find out…

Workout on an Empty Stomach

Training on an empty stomach has been heavily debated on over the years.

If we delve all the way back to how our hunter-gatherer ancestors lived, we may have an explanation to the debate.

Modern day research has found out that yes, this can indeed make you burn more fat, and we are beginning to discover the physiologic mechanisms behind this.

Burn More Fat

Exercising on an empty stomach can help you burn more fat by forcing your body to utilize fats as its main fuel source. After you eat a meal, glucose and glycogen, the storage form of glucose, is available for use.

Our body prefers to use it if it is there but if we intentionallyfast, the body has no choice but to burn fats instead.

A recent study found that men who fasted before moderate intensity cardiovascular exercise burned 20 percent more fat than those exercising with a fed stomach.1

Exercise Intensity

This is probably congruent to what our ancestors did, as they most likely did not have a local deli to get a meal from on the way to “work”.

Instead, they had to get up and chase animal down for breakfast.

How our body decides to burn fats in this scenario is based on the intensity and duration of exercise.

Our body chooses how to burn calories based on how intense an exercise bout is and how long we perform it for.

Power lifters and sprinters who exercise very intensely for less than 10 seconds burn almost no fat at all.

Endurance athletes who exercise at a moderate intensity burn mostly fat, which is what the ”fat burning zone” is. This is how our body works to be efficient with energy production and it is the key to utilizing this training approach.

Exercising on an empty stomach only makes sense if burning fat is your goal and you exercise at a moderate pace. That’s perfect for joggers and bikers looking tolose body fat.

Calories in. Calories out.

Keep in mind that being in a caloric deficit is more important than anything mentioned above.

Fat loss, first and foremost, is always dependent on the simple equation of calories in vs. calories out.

It is the determinant of whether one will burn fat or not.

Every diet and exercise approach for improved fat burning is dependent on playing “physiological tricks” on the body.

The success of any of those programs is still dependent on being in a caloric deficit – expending more calories than the amount of calories consumed.

Schedule Your Meals Around Fat Burn

Manipulating the timing of food intake is one of these strategies for improved fat loss and can work, but being in a caloric deficit is still a must.

The practical application of this concept is that you need to make sure that if you are exercising less intensely, you need to make sure the duration is increased to ensure a large overall caloric expenditure.

Conversely, if you are going to exercise super intensely because that is all you have time for or you just like that kind of training better, then exercising on an empty stomach may not be for you, unless you are willing to try something a little more extreme.

Optimizing Fat-Burning Hormones (Fasting)

Longer duration fasting can manipulate your hormones to allow for both extreme fat loss and increased muscle gain. 

When we are fasted for 24 hours and longer, which was probably commonplace for our nomadic ancestors, the way our body releases hormones starts to change.

Insulin levels decrease and growth hormone (GH) increases when about 3-5 hours after your last meal, after your body has done processing it.

When insulin levels are low, our body realizes we haven’t had food in awhile so we should start to gear up for relying on our fat stores.

Our whole fat burning factory gets revved up and fires on all cylinders for the sake of survival.

In addition, GH levels spike up tremendously in order to maintain the integrity of our muscles so they don’t break down.

They are a last resort and the last line of defense of our bodies ability to create energy, which is why it is only released after a prolonged fasted state.

While in this state, GH has been shown to be elevated by up to 2000%.2 If you eat a lot and then exercise very intensely, there will still be some extra GH flowing in you before it clears out.

You will give the body the stimulus and the nutrients to build muscle and you will have just burned a ton of fat while fasting for 24 hours.

This is physiologic mechanism is what those who participate in intermittent fasting try to take advantage of.

Those who like to exercise intensely can use this approach if they can bear fasting for the 24 hours it takes for GH levels to peak after a meal. And again, do not forget that overall caloric balance still needs to be in a negative if you want to lose weight!

If you have the discipline and the lifestyle that allows for fasting and exercising, you can take advantage of these physiologic tricks.

Both intense exercisers and lower to moderate exercisers can burn more fat with these fasted state exercising approaches.

Keep in mind that your training stimulus and your nutritional habits need to match as outlined in this article, otherwise you will get a drastically different effect than you are desire.

The days of hunter-gathering are over and we have food available at anytime.

We also don’t have to labor and battle for our lives anymore either so following this diet approach only makes sense if the exercise approach matches it.


  • Gonzalez JT, Veasey RC, Rumbold PL, Stevenson EJ. Breakfast and exercise contingently affect postprandial metabolism and energy balance in physically active males. Br J Nutr. 2013;110(4):721-32.
  • Ho KY, Veldhuis JD, Johnson ML, et al. Fasting enhances growth hormone secretion and amplifies the complex rhythms of growth hormone secretion in man. J Clin Invest. 1988;81(4):968-75.
Misato Alexandre


After making healthy living a priority, Misato lost over 20 lbs in less than 90 days. Instead of weight loss being a dreading experience, living the lifestyle of health and fitness granted her more happiness and joy than ever before. She co-founded Fitwirr to make health and fitness simple for everyone and share her tips through writing evidence-based articles on nutrition, weight loss, and exercise.

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