Fasted Cardio (Part 1): The Theory of Fat Loss Counter Point?

Sooner or later, someone was going to call me and my book out. Someone was going to challenge it. Someone was going to say, "Fasted cardio burns fat very effectively and is completed at a very low absolute intensity. Doesn't that contradict the theory of absolute intensity in your book?"

The truth is, my theory isn't 100% perfect and doesn't account for every little trick and technique. In fact, in the introduction of the book, I even point out that it will not be as all encompassing as the title makes it out to be. In a way, the theory is "wrong" when it comes to certain specific topics.

However, I knew all about fasted cardio long before I wrote The Theory of Fat Loss. If I had thought about it while I was writing the book, I would have included another "special topic" chapter like I had for several other subjects. Alas, it did not cross my mind at the time.

The good news is that I have this blog, so I can discuss it in as much detail as I want right here. So, in Part 1 of this series, I will explain what fasted cardio is (if you like extremely scientific discussions, click that link, and then read this equally scientific counterpoint; if you don't, read this simplified blog post) and how it is supposed to work. In Part 2, I'll give my take on it (and will subsequently explain why fasted cardio doesn't really contradict my theory at all).

So what is it? Fasted cardio is exercise where you perform some sort of steady state activity in the morning on an empty stomach (or in some practices, without ingesting any carbohydrates). The idea is that upon waking, you are in a fasted state, and thus you have more free fatty acids floating around to be utilized as fuel.

With low intensity cardiovascular exercise, your body uses a higher proportion of fat for fuel than with moderate or high intensity exercise, especially when those fats are in their free fatty acid state. So, the purpose of low intensity fasted cardio is to burn that fat directly.

There are many trainers and strength coaches out there that utilize fasted cardio as a tool to aid in their clients and athletes body composition goals. In fact, many of these trainers and coaches still swear that it is the best way to lose fat. That means that there is a TON of anecdotal evidence supporting fasted cardio.

I have my doubts about what is truly going on or if it really works better than anything else. Here are just a few comments that I have that I would like to leave you with before ending this post.

1. Isn't this basically the same argument that was made in favor of the "fat burning zone" on cardio equipment that has been COMPLETELY debunked time and time again? As Alan Aragon said in the second link I posted above,

"On the surface, it seems logical to separate carbs from cardio if you want a maximal degree of fat oxidation to occur during training. But, there’s the underlying mistake - focusing on stored fuel usage during training instead of focusing on optimally partitioning exogenous fuel for maximal lipolytic effect around the clock. Put another way, it’s a better objective to coincide your carb intake with your day’s thermic peaks, where insulin sensitivity & lean tissue reception to carbs is highest."

In other words, who cares what you burn during your workout? It is more important what happens throughout the entire day/week/month/year/etc.

2. Alwyn Cosgrove, perhaps the world's greatest fat loss expert, said this about it.

3. As I have been researching for this post, I thought more and more that the whole idea of "fasted cardio" (at least the fake version where it really isn't fasted because you get to have protein) is really a diet thing. Don't have a lot of carbohydrates. What a novel idea! Where have I seen that before? Oh right... just about everywhere.

4. If you read anywhere that fasted cardio works because your muscle glycogen is depleted in the morning, that is absolute BS. It is ridiculous to think that you go to sleep full of glycogen and then it all just disappears. It doesn't happen because it doesn't make any sense thermodynamically. You do have increased free fatty acids... but it has nothing to do with muscle glycogen depletion.

5. True fasted cardio (eating absolutely nothing) is going to have catabolic effects on muscle. You certainly don't want to lose muscle when you are losing fat (unless you are crazy or need to make weight for some sporting event). More on this later...

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Although it is my personal opinion that "fasted cardio" is all bark and no bite... I cannot say with 100% certainty that it doesn't work. However, as you read Part 2 of this series, you will realize why IT DOESN'T MATTER. In fact, just for the sake of discussion, I am going to assume that fasted cardio WORKS. That way, I can objectively examine it and put it up against The Theory of Fat Loss paradigm. Then, in part 3, I'll give you my real opinion of fasted cardio.


Read Part 2
Read Part 3