Fasted v Fed Cardio: Which is Better?

A debate which divides the fitness world. Fasted cardio. Is it better? Does it matter?

When approaching a coach or designing your own fat loss plan, cardio is something which will almost certainly have to be implemented at some point, if you aren't already doing it for the cardiovascular benefits. Energy expenditure is another variable we can manipulate to influence weight. Adding cardio when hitting a plateau allows us to keep food higher, by increasing calories burned.

The gym-bro logic behind fasted cardio being superior, is that, without food in our system, our body will go straight to its fat stores to burn as fuel. Others will claim that this theory is outdated, and cardio will influence fat loss in the same way regardless of what time it is completed.

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Fasted

What is it? Fasted cardio is done shortly after waking, before consuming your first meal. True fasted cardio would mean no coffee or supplements (such as BCAAs), only water prior due and during. There are no rules on what cardio should be performed, whether it be a brisk walk outside or the stairmaster. We would however advise avoiding sprints and HIIT if trying to gain/maintain as much muscle as possible during a cut.

Pros. There are plenty of benefits to doing your cardio first thing. It starts your day on a positive note. There are plenty of mental benefits to knowing that you've achieved something early on, and it may increase motivation levels for the rest of the day. Also, it pushes meals back for a shorter eating window. This can help with controlling appetite in a diet.

Scientifically speaking, growth hormone is higher and insulin lower in the morning, creating a somewhat better environment for fat burning.

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Fed

What is it? Fed cardio is any cardio done following at least one meal. In its own session or post-workout is best. While pre-workout cardio can be a good warm up tool, performing cardio intensely enough to illicit fat burn will negatively impact the successive weight training session, which is more important for most to prioritise.

Pros. Fed cardio can also have its benefits. If energy levels are incredibly low first thing in a morning, the quality of cardio may be improved after eating, so more calories will be burned. It may also fit in better with your schedule, depending on work hours, to do cardio on an evening.

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Debunking the Myths

The problem with the argument that fasted cardio burns body fat, and not stored carbs, is that we are usually not as 'fasted' as we think. Glycogen stores will not have been completely depleted over a period of 8 hours of so while sleeping, especially if you eat carbs later in the day or are only in a moderate deficit. Intermittent fasters and bodybuilders at an extreme low level of bodyfat and intake may be an exception to this rule. Remember that, for those who are incredibly lean, the body is particularly vulnerable to breaking down muscle. EAAs may help with muscle retention.

EAAs may assist muscle retention and recovery in a deficit.

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Conclusion

Ultimately, rather than inconveniencing yourself in the belief that that fat oxidation might be increased by a tiny percentage by, do your cardio at a time that works well and you will find most enjoyable and easy to keep up. Remember that cardio at any time of day will be burning calories and increasing your deficit. Energy balance is what will ultimately control whether the number on the scale goes up or down, don't worry too much about the complexities until it is necessary!

Burning more calories will affect energy balance regardless.

About the Author

Savannah Westerby, BSc Sport and Exercise Nutrition. IG:@savannahwesterby
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