Fasted cardio isn’t your best friend

Bodybuilders and other fitness enthusiasts are always looking for better ways to target and burn fat.  Fasted cardio is one of those things that is constantly discussed.  The first article that comes up when you search for fasted cardio is one from  Written by a self identified “expert”, she goes on throughout the article to say that adding fasted cardio to your routine will help you target those “stubborn” areas.  Unfortunately its just another blog that is hardly supported by much science.  So do you really want to know if fasted cardio results are actually beneficial to add to your workout routine?

What Is Fasted Cardio?

There isn’t really a formal fasted cardio definition.  Fasted cardio refers to doing cardio in a fasted state, so in the morning when you wake up without consuming any calories and doing cardio would be considered “fasted cardio”.  Just having an empty stomach doesn’t quality as a fasted state.  Your generally fasting upon waking up in the morning since you haven’t consumed calories over the course of the 8 hours you slept.  The theory is that in a fasted state your body burns more fat so doing fasted cardio will result in greater fat loss than if you had consumed food.  Well what does all the research actually say?

A brief look at some research

Effects of carbohydrate ingestion before and during exercise on glucose kinetics and performance

The study linked above tested cyclers who were both fasted and those who consumed carbohydrates throughout the workout.  The study results showed total fat oxidation was no different between the two groups but the group that ingested the carbs performed better.

Lipolytic suppression following carbohydrate ingestion limits fat oxidation during exercise

This is another study that people tend to say supports the fasted cardio theory.  This study showed a 22% suppression is lipolysis in the group that wasn’t fasted in a group of six cyclists they tested.  Fat oxidation remained the same between the two groups until the fasted group met 80-90 minutes of cycling where just then did the fasted group actually have greater fat oxidation.

What do these two studies tell us?

I have bad news for all the supporters of fasted cardio.  Although fasted cardio breaks down fat in larger amounts for energy, your body cannot use this excess energy because its too abundant.  When your body has free fatty acids it cannot use for energy, it will re-esterify straight back into the adipose tissue completely negating any benefit of the break excess fat break down. So what did I just say?

Thats right, your going to break down the fat but since that fat can’t actually be used for energy your body reabsorbs it.  There is another list of studies that further outline the many things that occur in your body when you do cardio in a fasted state that have no benefit.  An analysis of these studies can be found at this link.

So what should I do to maximize fat loss?

One important thing that is learned about fasted cardio is the increased breakdown of fat that CAN be used for energy.  Intermittent fasting  uses this to its advantage and science shows this actually works.  As far as cardio goes, your better off training in a non-fasted state because you can train at a higher intensity and have better overall benefits from the exercise itself.  Want to challenge this article?  Leave a comment and battle it out with us! Just make sure you read all of our supporting links before telling us we are wrong :=)

9 Comments Add yours

  1. Nick says:

    Interesting. I’ve also been contemplating doing exercise when fasting. However, I think you need to be fully ketogenic in the fist place in order to get the full benefit


    1. purebcaa says:

      It’s very possible that being in a ketogenic state could be more effective when fasted since your body is already fully fat adapted. We will look and see if there is any research that proves this.


      1. Nick says:

        Thanks. I will look forward to seeing your findings.. :))

        Liked by 1 person

  2. Interesting article. I have to respectfully disagree. I do mixed method training. I do BOTH fasted and fed training. Here’s where I think your logic falls short. YES, we can IF and burn more fat during the day, HOWEVER, the rate of caloric expenditure is very low at rest. If we exercise FASTED, the rate of caloric expenditure is higher AND we “catch up” fat supply with fat demand much better. I did a cutting-edge video on this choke-full of research studies-

    Liked by 1 person

    1. purebcaa says:

      Hey Ivan we appreciate the comment. There is a lot of research surrounding fasted cardio and personally we think its often times conflicting. As you stated in your video the research is more than just about the results its about the entire study (study design, methods, etc). We cannot deny that there could be times where fasted cardio could be your best option in terms of fat loss. In one of the studies you linked on the video they used specially designed meals to ensure proper energy balance. There may be very specific conditions in your body that need to be met in order for fasted cardio to provide greater efficacy. I myself (zack) exercise fasted because I Intermittent Fast and the only time I can workout is in the morning and it may or may not be ideal. Based upon the full text articles on either side of the argument we still believe that there is more science to support the lack of evidence.

      Liked by 1 person

      1. Great points. Saying there is more science to support lack of evidence to me is like saying, we need more research. Well if that’s the case, this case can be made for pretty much all topics of investigation as there will always be the need for more evidence. But overall, the research strongly suggests a metabolic advantage of fasted training vs. fed training. Now, there are layers to this such as post-prandial timing. If one waits 3-4 hours post-prandial, this can drop insulin levels to a somewhat comparable level to fasted cardio. Also, bear in mind I did say that I do BOTH. I know the effectiveness of fed training as I am also a triathlete and understand the nutritional science and importance of glycogen sparing, which can be effectively done via feeding before, during and after training. Fasted training can create “adaptation” that may relegate it ineffective as really with any other mode of training. But aside from the fat loss effects, have you looked at other variables of fasted training? In my video, some of my references point out it has a favorable post-meal fat-partitioning effect. In other words, less fat is stored after a fasted workout. On the flip side, working out after a meal better balances blood sugar. So this is why I like doing both methods. They both have differing adaptations.


      2. purebcaa says:

        If we are speaking in context of simply fat loss I think we are both correct in what we are saying. While there may be a metabolic advantage to fasted cardio (more calories may be burned), this metabolic advantage does not automatically mean fat metabolism is elevated. The research shows that Lipolysis is suppressed in the presence of carbs (which would lead someone to believe its not as effective). The research also shows fat oxidation is around the same comparing the two up until a certain point (if fat oxidation is the same then the body must reabsorb it). For a regular person (not people who understand this science) I firmly believe fasted cardio is a waste of time. There are a ton of variables that play into stuff like this I think we both can agree on that. Once you understand those variables there are plenty of ways to use that to your advantage. This goes for a lot of things with exercise and nutrition. You make some good points in your video, however, and I will continue to research fasted state exercise.


      3. Ivan Blazquez says:

        Well said. While the jury may still be out, I believe fasted cardio does burn more fat. Now this of course is just my opinion. But I have read more studies indicating and concluding this than not. Personally fasted cardio leans me out more than fed cardio. But again, I do both. So I like my odds of experiencing an optimization of a greater variety of adaptations. In fact, there’s new research called “Train low, race high.” So it appears fasted cardio is being investigated for performance adaptations as well.

        Liked by 1 person

      4. purebcaa says:

        Interesting I’ll have to check that out!


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