This belief has been around since the 1980s, but new research shows us it’s not true.

does fasted cardio burn more fat

Written by Russ Howe PTI, and most recently updated 1 day ago.

5 min read

Fasted cardio has been a thing since the 1980s.

It occasionally makes a comeback in the fitness world, most recently when Jennifer Lopez’s personal trainer called it “the secret to her great body” (ignoring the fact that she’s only recently started doing it but has been in amazing shape for over 30 years).

The boffins who created old-school training plans believed that training first thing in the morning on an empty stomach would force the body to burn through fat reserves, creating greater weight loss results for the trainee.

However, new research shows us that our old beliefs about fasted cardio burning more fat are not true.

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fasted cardio myth

Some fitness theories are silly as fuck, but this one actually makes a lot of sense.

In the absence of readily available food, your body will have no choice but to tap into your existing energy reserves (body fat) to use for fuel during a fasted cardio workout.

This is why thousands of people drag themselves out of bed at Fuck O’ Clock in the morning and pound the treadmill like an angry mother taking a faulty item back to a store.

I’ve done fasted cardio lots of times over the years, and I really enjoy it, but that doesn’t change the fact that our old theory is dead wrong.



does fasted cardio burn more fat

I’d love to think that I could “trick” my body into fat burning mode, but it turns out the body is smarter than we think.

The belief that “fasted cardio burns more fat” was first challenged in a study published in the Journal of Applied Physiology back in 2000.

This trial caused uproar in the fitness community at the time, as it had long been accepted as norm at this point, but the researchers were able to clearly show that trainees who performed fasted cardio did not see greater fat loss results. In fact they burned slightly less than trainees who trained in a fed state (albeit the differences were minor). (1)

a graph showing the difference in 24 hour calorie burn between fasted cardio and fed cardio

Even though it was a well-conducted study, many people in the fitness sphere decided to simply ignore these findings, because it was just one study and it flew in the face of convention.

However, they were wrong.

In the years which have passed since then we’ve had a mountain of new studies re-confirming what the original researchers stated back in 2000: Fasted cardio does not burn more fat!

The pick of this research was published in the Journal of Strength and Conditioning Research in 2011. This huge meta-analysis combined the results of 33 other studies on the topic and concluded that fasted cardio does not burn more fat. The American Council of Exercise has since re-confirmed these findings, and more recently performed studies have, too. (2, 3, 4)

It turns out the human body is clever as fuck.

If it’s forced to burn through fat reserves during an early morning workout, it will counteract this by switching to using carbohydrate reserves later in the day, whereas someone who trains in a fed state will burn through their carb reserves in training and their body will switch to burning through fat later in the day. It’s all about energy balance, and we don’t get the luxury of picking and choosing.



does early morning fasted cardio burn more fat

The main thing this tells us is that you can choose whichever type of cardio you prefer.

The difference in results between fasted cardio and fed cardio are tiny, so go with the one which you find easier to stick to in the long-term and you’ll see better results that way.

Also, when I speak about fasted cardio I mean cardio in the more traditional sense (i.e. steady state cardio), not HIIT. If we wanted to do this comparison using HIIT then you definitely don’t want to be training in a fasted state, because HIIT relies on carbohydrates for fuel, so performing it in an unfed state would lead to poor performance. (5, 6)

I hope you enjoyed the read.

References:

  1. Febbraio M. A., et al. Effects of carbohydrate ingestion before and during exercise on glucose kinetics and performance (2000).
  2. Schoenfeld B. Does Cardio After an Overnight Fast Maximize Fat Loss? Str Cond J (2011).
  3. Hackney K.J., et al. Timing Protein Intake Increases Energy Expenditure 24 H After Resistance Training. Med Sci Sports Exerc (2010).
  4. Paoli A., et al. Exercising Fasting Or Fed To Enhance Fat Loss? Influence Of Food Intake On Respiratory ratio And Excess Post Exercise Oxygen Consumption After A Bout Of Endurance Training. Int J Sport Nutr Exerc Metab (2011).
  5. Wright D. A., et al. Carbohydrate feedings before, during, or in combination improve cycling endurance performance. J Appl Physiol (1991).
  6. Schabort E. J., et al. The effect of a preexercise meal on time to fatigue during prolonged cycling exercise. Med Sci Sports Exerc (1999).

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I’m Russ. I’ve been a personal trainer since 2002, and I own russhowepti.com.

My job is to simplify fitness for my readers.

I send out free fitness tips to over 100,000 men and women every week, all in the same no-nonsense style as the article you’ve just read, so if you enjoyed reading it be sure to jump on my email list below.

2 responses to “Does Fasted Cardio Burn More Fat?”

  1. Melissa avatar

    Great info Russ! I use If but make sure that it is not during my fast because I really go heavy.

  2. Faye avatar
    Faye

    Fantastic breakdown, learnt so much from this!

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