The Death of Fasted Cardio

The use of fasted cardio has been a common practice in the fitness world for well over a decade. A lot of people swear by fasted cardio, with the idea that a fasted state, in the absence of carbohydrates and the dreaded insulin hormone, will create a superior environment for fat loss.

When you look at it practically and evidently, it doesn’t really make much sense. Any potential rationale behind it is severely short sighted, or won’t cover the mechanistic reasons to why it’s effective.

If we look at fat loss mechanistically, we lose body fat when we are in an energy deficient state. That means the total some of energy we are burning as a physiological system is greater than the energy being consumed through food and drink.

When we don’t supply the body with sufficient energy from the diet, it needs to pull energy from somewhere else. In this situation stored body fat can be utilized to support the energy demand imposed on the body. If we create this environment consistently, an individual will lose body fat over time.

For fasted cardio to be superior, it must work in a manner that influences energy balance outside of simply adding to one’s daily energy expenditure.

Does it increase total daily energy expenditure?

Does the superior partitioning of fat lead to great fat loss during training?

Does it possibly suppress appetite to control energy balance better?

When we look at the research, none of these suggestions are supported.

There is no evidence that fasted cardio increases daily expenditure. There is actually suggestions that total data energy expenditure could decrease when fasted cardio has been performed.

The idea that fasted cardio may “burn” more fat in comparison to fed cardio is like looking at something large through a microscope, and isolating variables that don’t really matter. Just because fat partitioning is greater during fasted cardio does not make the practice exempt from the laws of energy balance. The sum of energy going in verse the sum of energy going out of the biological system is still the overarching variable here. What you burn for fuel and when you do the activity means nothing in the bigger picture.

Finally, fasted cardio does not decrease one’s appetite. There is actually evidence to suggest that it may increase total energy consumption over a day in some individuals.

When you look at the evidence and understand the mechanisms of fat loss, fasted cardio gets a big thumbs down from me. It shouldn’t be something we are forcing ourselves to do. In a lot of cases the extra 1–2 hours of sleep one may get, is way more beneficial than forcing ourselves to hit the pavement, or the treadmill in the early AM. Its way more practical to do your cardio at time that conveniences you and ensure you are managing your energy balance to create an energy deficit.

Thanks for reading.