Fasted Cardio: Does it Burn More Fat?
Does fasted cardio REALLY burn more fat than regular cardio?
Jennifer Lopez says it does. Case closed!
Not really, of course.
But J-Lo did recently credit her new routine of early morning fasted cardio as being “the secret behind her great body”, and it’s caused lots of people to try following suit so today I’m going to get to the bottom of this subject for you ONCE AND FOR ALL.
First we have to deal with some flawed logic…
Given that J-Lo only recently started doing fasted cardio, this is obviously NOT the reason she’s in great shape. After all, as a former professional dancer, she’s been in great shape for 25 f**king years.
Now that’s out of the way, let’s move on to the science behind it…
Why Do We Think Fasted Cardio Is Better For Fat Loss?
The theory behind fasted cardio is rock solid.
Our body likes to burn carbohydrates for fuel, so by training early in the morning when there are very few carbs in our system, we’ll have no choice but to use fat for fuel instead.
Calories be gone!
It makes perfect sense. After all, your body has got to give you something to push through your training, otherwise you wouldn’t be able to do it.
Therefore we’re prepared to drag ourselves outta bed at F**k O’ Clock every day, when even the neighborhood rooster asks why we’re up so early, all in the name of pounding the treadmill for some extra fat loss.
What Does Science Say?
Unfortunately, none of the above is correct.
If there’s one thing the research on fasted cardio shows us, it’s that the human body is a wonderful, very complex machine!
A 2000 study published in the Journal of Applied Physiology found that performing fasted cardio caused no improvements in overall fat loss. At the time, fasted cardio was generally believed to be superior, so these results were startling. (1)
But new research has since shown us why…
One of the key studies in doing so was Dr. Brad Schoenfeld’s meta-analysis on on this topic, which was published in the Journal of Strength and Conditioning Research in 2011. (2)
A meta-analysis is where researchers compile the results of every study ever performed on a particular subject (in this case; fasted cardio), to see if they can form a general pattern with the results. This comprehensive meta-analysis doubled-down on the previous research, stating that fasted cardio is not superior for fat loss.
It’s a conclusion the American Council of Exercise have since confirmed, and more up-to-date studies performed after Dr. Schoenfeld’s review have re-confirmed, too. (3, 4)
So why is this the case?
Well, it all comes down to energy balance (calories in vs calories out). I discuss energy balance in more depth in this post, so go read it, but the crux of the matter is that being in a caloric deficit is the most important factor in achieving weight loss – not which macronutrient we use for fuel during the training itself.
Meaning if two identical guys both ate 2000 calories per day, with one performing fasted cardio and the other doing regular cardio, they can expect the results to be the same.
It appears the body is capable of second-guessing us and adapting to its surroundings, so while we will definitely tap into our fat stores during a fasted cardio workout, that doesn’t mean we’ll burn more fat over the course of the entire day. In fact, it seems we will switch to burning more carbohydrates later on in a bid to restore balance.
Meanwhile, the guy who performs regular cardio will burn more carbohydrates during training, but his body will burn more fat throughout the day to keep the balance.
Obviously, this post relates to steady state cardio (a.k.a. aerobic cardio). If you perform HIIT, it goes without saying that you should definitely grab some food prior to training. After all, HIIT relies on our carbohydrate stores and its benefits hinge on our ability to be explosive. Performing HIIT without adequate fuel will lead to sub-maximal performance levels, and negate many of the results it offers. (5, 6)
Hopefully by now you’re starting to get a feel for the big picture here. There’s one more thing I want to touch upon before we move on…
There was a headline in 2019 that caused fasted cardio to make a brief comeback, after researchers from the UK suggested that “skipping breakfast before exercise resulted in greater fat loss”. In truth, this study was so full of holes it could’ve doubled as a cheese grater. They found that participants who ate one fewer meal (i.e. they skipped breakfast) lost more weight.
It wasn’t because they exercised on an empty stomach… it was because they ate one less meal! Those calories were never replaced, so we had one group consuming less food than the other! Sadly, this poorly conducted study received a lot of media attention at the time, and misled a whole bunch of people. (7)
So J-Lo Is Dead Wrong?
Fasted cardio will certainly burn fat, and there’s nothing wrong with doing it. Heck, I’ve done it myself. I feel LEAN AF after I get off that bike first thing in the morning…
But decades of clinical trials prove you won’t lose more body fat versus doing regular cardio, so just do the one you personally prefer.
Of course, in situations like this I never blame the celebrity.
They’re regular people, and they get sucked into fads and myths just like anyone else.
Heck, a year ago they were all paying Gwyneth Paltrow absurd amounts of money for special rocks to shove up their hoo-haa.
But I’ll tell you who I do wanna slap…
When personal trainers and “fitness influencers” (NOTE: not a qualification!) pedal outdated advice to clients and followers, it’s no wonder people are confused, and it happens all too often…
Go watch The Perfect Physique, currently streaming on Netflix. You’ll see a bunch of fitness models discussing their training routines.
During the course of the show, we get this corker:
These are FITNESS PROFESSIONALS!
What’s perhaps even funnier, is that later in the show the same person talks about how you need to eat a meal every 2 hours to avoid going catabolic. If we lost muscle that quickly, we’d all be dead. Also, do they not realize they’re willingly putting themselves into a fasted state for 8 hours at night then jumping on a motherf**king treadmill?!
Uncle Russ has officially ran out of evens to can’t.
So yes, Jennifer Lopez is incorrect when she states that fasted cardio is better for fat loss. But I don’t blamer her at all. I blame motherf**kers like this.
If you’ve enjoyed this breakdown on fasted cardio, get on my email list and check out my workout programs. See you next time out.
- Febbraio M. A., et al. Effects of carbohydrate ingestion before and during exercise on glucose kinetics and performance. (2000)
- Schoenfeld B. Does Cardio After an Overnight Fast Maximize Fat Loss? Str Cond J. (2011)
- Hackney K.J., et al. Timing Protein Intake Increases Energy Expenditure 24 H After Resistance Training. Med Sci Sports Exerc. (2010)
- 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)
- Wright D. A., et al. Carbohydrate feedings before, during, or in combination improve cycling endurance performance. J Appl Physiol. (1991)
- Schabort E. J., et al. The effect of a preexercise meal on time to fatigue during prolonged cycling exercise. Med Sci Sports Exerc. (1999)
- Edinburgh R. M., et al. Skipping Breakfast Before Exercise Creates a More Negative 24-hour Energy Balance: A Randomized Controlled Trial in Healthy Physically Active Young Men. The Journal of Nutrition. (2019)