Should You Do Fasted Cardio When Bulking? (Science-Backed)

So, it’s bulking season and you are looking to put on as much lean mass by eating in a caloric surplus to provide your muscles a strong environment to grow.  

Although it’s not necessary in order to build muscle, many will still incorporate cardio sessions during a bulk to maintain their cardiovascular health and help burn unwanted fat. But does the timing of your cardio session have any impact on the success of your bulk?

In order to answer this, I’ve done the research on the impact of cardio in a fasted vs. fed state on body fat and muscle mass.

Should you do fasted cardio when bulking? No, there is no benefit to doing fasted cardio when bulking. Performing cardio in either a fed or fasted state will not change the resulting gains or losses of body mass and therefore you should only do fasted cardio when bulking if it is a personal preference.

In this article, I’ll discuss the purpose of a bulk, debunk common myths about fasted cardio and share some considerations for when implementing fasted cardio during a bulk.


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What is a bulk?

The purpose of a bulk is to increase your body mass. To do this, a bulk requires eating in a caloric surplus so that your muscles have a strong environment to grow.  

There are two ways of doing this.

The first is a ‘dirty bulk.’ 

This is when you eat whatever you want, and as much as you can, to gain weight as fast as possible. Typically this includes a lot of unhealthy junk food. With a dirty bulk, a lot of the weight gained will be from fat. Dirty bulking provides all the downfalls to our health of adding unwanted fat and additionally covers up whatever muscle has been gained. 

The alternative, and the recommended method for bulking, is a ‘clean bulk.’ 

With a clean bulk, the objective is not to just put on body mass in general, but to increase our lean mass, or muscle mass and limit the amount of body fat we add in the process.  This would look like a moderate, controlled caloric surplus comprised of mostly clean foods. 

Why should you implement cardio during a bulk?

 


 

So, if the purpose of a bulk is to add muscle mass, why would someone continue to implement cardio at all? 

Cardiovascular training improves the heart’s ability to pump blood and increases oxygen uptake into cells. Strenuous weight training can be aerobically taxing and therefore having an efficient, strong heart will allow you to train harder to build more muscle and burn more fat. 

Related Article: Can Cardio Burn Muscle? (Yes, Here’s How)

By implementing light to moderate cardio sessions, this will not only help with burning unwanted fat that may have been gained from being in a caloric surplus, but it also makes one’s calorie consumption potential greater which will help in building more muscle (because you can simply eat more). 

So now that we understand one purpose of cardio during a bulk is to burn unwanted fat, will performing cardio in a fasted state burn more fat?

Related Article: Lifting Weights While Fasted: Should You Do It?

Does fasted cardio burn more fat?

 


 

Current research shows that training in a fasted state does not burn more fat than performing cardio in a fed state (Paoli, 2011).

Fasted cardio is when you perform cardio in a fasted state, typically in the morning before consuming any calories. Essentially, you’re on an empty stomach.

Previous research showed that when you train fasted, more fat is burned during the training session as compared to training after consuming food (Horowitz 1997). 

Related Article: The Best Pre-Workout For Fasted Cardio

However, current studies that look at the amount of body fat that is burned in the 24 hour period following a cardio training sessions conclude that training in a fed state burns more fat than doing cardio in a fasted state for up to 12 hours post exercise (Schoenfield, 2014).

The results of a study that looked at two groups of women, both in a 500 calorie deficit and eating the same food, half of which did their cardio fasted, the other half fed showed that there was no difference in fat loss amongst the two groups (Schoenfield, 2014).

Related: Check out our article on the 7 Best Breakfast Ideas (With Calorie Breakdown).

Now, let’s remember that the purpose of a bulk is to lay down lean mass by eating in a caloric surplus (consuming more energy than you are burning). Research also shows that performing fasted cardio has greater appetite suppressant effects than performing cardio after having consumed a meal (Deighton, 2012). 

So if you are looking to implement fasted cardio into your training regime while bulking for the purpose of burning unwanted fat, you should not do fasted cardio. 

Related Article: What Cardio Should You Do When Bulking? (3 Options)


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4 Important Considerations for Cardio During a Bulk

Now that we understand what bulking is and the concept of fasted cardio, there are a few things you should always take into consideration when implementing cardio if you are bulking. 

1. Are you in a caloric surplus? 

Although it is possible to get stronger without a caloric surplus, the purpose of a bulk is to provide an optimal environment for your muscles to grow.  An optimal environment is one with lots of food or when you are in a caloric surplus. A caloric surplus is when the amount of calories that we consume is higher than the amount of calories we burn. In a caloric surplus, our body mass increases. 

Regardless of whether or not our daily caloric intake puts us in an overall surplus or deficit, after we eat a meal, we are in a caloric surplus until our body utilizes the energy. Then after a while of not having any food, we’re in a deficit. 

If you are considering doing fasted cardio while bulking, you will need to ensure that you are in a large enough caloric surplus so that when you are performing the cardio, you still remain in a surplus and your body has energy to burn. A sufficient caloric surplus would be about 10%, meaning that you consume 10% more calories than you burn in a day.  To calculate how many calories you theoretically burn in a day, you can use an online calculator like this one

For example, if you burn 2000 calories in a day, to put yourself in a caloric surplus of 10% you would need to consume 2200 calories per day. 

If we don’t maintain a sufficient caloric intake, we run the risk of our body resorting to stored protein (muscle) as usable energy. This would be very counterproductive to the goals of a bulk. 

Related Article: Sprinting On Treadmill vs Outside: Which One Is Better?

2. The frequency and intensity of your cardio sessions

Cardio does not have to be done all the time in order to be beneficial to our health and burning unwanted body fat. Implementing cardio into your
resistance training routine, 2-3 days a week for 20 minutes would be sufficient. 

3. What is your personal preference?

It’s common for people to want to do their cardio sessions first thing in the morning to get it out of the way with.  If this is the case, some people don’t have an appetite first thing in the morning, or prefer to feel lighter for their sessions. 

If this sounds like you,  I recommend trying to consume coconut water, natural fruit juice or baby food as soon as 30-45 minutes before your cardio session to ensure your body has adequate fuel available. 

And yes, baby food is a great way to get in some quick carbohydrates before a training session as they are easily digestible, tasty and easy to have on hand.

Related Article: Can You Eat Anything While Bulking?

4. Track your progress 

To make sure that you are gaining mainly lean mass (i.e. muscle) and to avoid adding unnecessary body fat, you want to aim for a weight gain rate of about 0.5-1lb per week. Without tracking your progress, it will be difficult to know if you are gaining weight too fast, or if you are at risk for losing muscle mass. 

Related Article: The Top 5 Cardio Machines That Are Good For Weight Loss

Final Thoughts 

The best way to bulk is to increase our lean mass (muscle) and limit the amount of body fat we add in the process. The most effective and efficient way to do this is to eat in a controlled caloric surplus. Implementing cardio can help ensure that any unwanted body fat is burned, improve heart function which will allow you to train harder and lay down more muscle, as well as increase your calorie consumption potential. 

There is no special benefit to fasted cardio for fat loss and therefore should not be implemented during a bulk. Although there are no detriments to fasted cardio during a bulk so long as you are eating in a sufficient caloric surplus, it could affect your appetite and ability to consume the required amount of food to lay down lean mass. 


About The Author

 


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Maggie Morgan is a level 1 PN certified nutritionist who specializes in sport, exercise and performance nutrition, a strength training coach, and an elite level athlete. Maggie has competed in bodybuilding, and is an international-level powerlifter. Currently undertaking her Masters in Counselling Psychology, Maggie is not only able to lead others in strength and aesthetics through her personal experiences and scientific nutritional foundations but additionally by addressing the psychological and behavioural implications of exercise and nutrition. Through her writing and work with clients, Maggie works to provide information that’s responsible, rational and backed up by research, science and fact within the health and fitness industry.


References

Deighton, Kevin, et al. “Appetite, Energy Intake and Resting Metabolic Responses to 60min Treadmill Running Performed in a Fasted versus a Postprandial State.” Appetite, vol. 58, no. 3, 2012, pp. 946–954., doi:10.1016/j.appet.2012.02.041.

Horowitz, Jeffrey F., et al. “Lipolytic Suppression Following Carbohydrate Ingestion Limits Fat Oxidation during Exercise.” American Journal of Physiology-Endocrinology and Metabolism, vol. 273, no. 4, 1997, doi:10.1152/ajpendo.1997.273.4.e768.

Paoli, Antonio, et al. “Exercising Fasting or Fed to Enhance Fat Loss? Influence of Food Intake on Respiratory Ratio and Excess Postexercise Oxygen Consumption After a Bout of Endurance Training.” International Journal of Sport Nutrition and Exercise Metabolism, vol. 21, no. 1, 2011, pp. 48–54., doi:10.1123/ijsnem.21.1.48.

Schoenfeld, Brad Jon, et al. “Body Composition Changes Associated with Fasted versus Non-Fasted Aerobic Exercise.” Journal of the International Society of Sports Nutrition, vol. 11, no. 1, 2014, doi:10.1186/s12970-014-0054-7.