Fasted Cardio (Part 3): The LAZY Man's Dieting Gimmick

Part 1
Part 2

This is the finale to the 3 part fasted cardio series. In Part 1, I introduced us to the concept of fasted cardio for selective fat loss. In Part 2, I compared the effectiveness of fasted cardio as a fat loss tool to the new paradigm from The Theory of Fat Loss: A New Paradigm for Exercise and reached the conclusion that it may be a useful tool... but only as an adjunct to training assuming that it doesn't interfere with recovery from a person's primary training program.

Interestingly, Eric Cressey just wrote an article about the problems associated with "adding" to weight training programs, and he hit on a great point about it. I suggest checking it out here.

But anyway... in this post I will simply reveal to you that fasted cardio is nothing more than an overblown and overpracticed manipulation of your DIET and not really anything special.

Fasted cardio is said to work because when you wake up in the morning, you have many free fatty acids available to be used as fuel. In a non-fasted state, you have less free fatty acids available, and your body will thus use a higher percentage of glucose for fuel. Low intensity aerobic exercise (rather than high intensity exercise of any sort) isn't intense enough to require that you burn glucose for energy. So, when you exercise at a low intensity, you can use a slower burning substrate, fat. Combining this low intensity exercise with the increased free fatty acids that are available gives you a way to increase how much fat you burn DIRECTLY with exercise.

The other important point I need to make is that "fasted" cardio isn't often performed in a truly fasted state. In fact, if it is performed completely fasted, there will be a loss on muscle mass because protein will also be metabolized for energy. That is obviously not a desired outcome. Therefore, many people that recommend "fasted" cardio for fat loss also recommend consuming a small portion of protein before hitting the roads. That way, the catabolic effect of exercise on muscle mass is countered. This portion of protein is said to have a very minor effect on how much fat is burned during exercise, by the way. Insane, right? Who would have thought that protein doesn't increase your blood sugar?

Now, I need to describe a few things before returning to my point about the effectiveness of fasted cardio. I will eventually bring this all full circle, so keep focused.

If you know anything about aerobic exercise equipment, you will know of something called the "fat burning zone." This is the zone that corresponds to the intensity at which you are supposed to burn the greatest percentage of fat during exercise. In other words, it isn't a very high intensity. This "fat burning zone" has been discussed time and time again by many a fitness professional to be utterly useless. Why? It doesn't matter all that much what energy substrate you use for fuel during exercise.

If you burn 100 calories from fat instead of 100 calories from glucose, what happened to that glucose that you could have burned instead? It is still there being stored in your body either as glycogen or eventually as fat, right? It doesn't just disappear. So, you burn some fat, but you still have some glucose... what's the difference? Not all that much.

Our real goal should be to burn as much fat as possible throughout the day while at the same time preventing sugar from being stored in our bodies as fat. How do we do that? We combine high absolute intensity training with smart dieting practices. Training at a high absolute intensity will result in the greatest increase in your body's metabolism throughout the day and will result in a vastly increased daily energy expenditure. If you don't eat and drink a lot of terrible foods and drinks (basically all that stuff that is high in sugar/carbs), then you won't be storing all that garbage as fat. Does that make sense?

Now, I have gotten away from the main point of this entry a little bit, but I did it to elaborate upon a point. That point is two-fold.

1. It doesn't really matter what substrate you use during exercise. The purpose of exercise is to ramp up your metabolism. This is best accomplished with high absolute intensity activities.
2. If you don't eat a lot of carbohydrates, your body won't have high blood sugar levels and thus won't be driven to store the sugar as fat.

So... let's take that a step further. If we don't consume a lot of carbohydrates, then we won't have much glucose available to be used as fuel throughout the day. That means we'll also have an increased utilization of FAT as an energy substrate ALL THE TIME... meaning we will be burning fat LIKE CRAZY while we just sit around and do nothing (or exercise at a low intensity).

What does that tell you about fasted cardio? It isn't about the cardio. It is just diet manipulation for people too lazy to manipulate their own diets. They just use the fact that they were unconscious for 8 hours (and therefore couldn't screw up their diets by eating) to put them in a state of high fat utilization. Then they just throw in a little cardio to increase that fat burn just a little bit (which, as I already addressed, doesn't really matter all that much).

So, does it work? Yes, it works... but that is only because they increased their intensity from resting to active. It is not a very useful replacement for high intensity activities because it has minimal effect on speeding up your metabolism throughout the day. However, as I stated in part 2, it might be useful as an adjunct to an already sound training program as long as it does not interfere with recovery. Of course, if you eat a healthy diet that doesn't spike your blood sugar, it really wouldn't matter when you do this cardio, now would it? You'd be primed to burn extra fat all day (by just sitting there doing nothing or with low intensity exercise)... but that just makes too much sense, doesn't it?

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... and of course, comments are always welcome below, so please share your thoughts on fasted cardio below.