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EXPOSED - Fasted Cardio is a Waste of Time and Effort – It DOESN’T Work!

Jamie Lloyd

By Jamie Lloyd

Jamie Lloyd is an award winning Fit Pro, international best-selling author and fitness writer based in SW London…
Read more.

We've all heard it time and time again, the theory that doing cardio in a fasted state sends your fat burning into overdrive – but does it? Jamie Lloyd explains…

Back in the 90’s everyone was hitting the treadmill in the gyms whilst skipping brekkie!

EXPOSED - Fasted Cardio is a Waste of Time and Effort – It DOESN’T Work! By Jamie Lloyd

The strategy became popular with bodybuilders and other physique athletes striving to get as lean as possible. After all, who wouldn't want to burn more lard while expending the same amount of effort?

I'm sorry to say it, but the whole starving yourself before beasting yourself on the cardio machines was a big mistake.

Here's why…

Measuring Your Metabolism and Doing Cardio

calorie count on exercise bike

Firstly, it's short-sighted to simply look at the number of fat calories burned in an exercise session. Your metabolism doesn’t just stop after you leave the gym you know…

Rather, the body continually adjusts its use of fat and carbohydrate for fuel depending on a variety of factors and keep burning calories once you are done!

Generally, if you burn more carbohydrate while exercising, you'll ultimately burn more fat in the post-workout period and vice versa.

So what’s the Truth?

"Who cares if you burn 400 calories while exercising, if an hour later, the ratio shifts to a greater carbohydrate utilisation and more calories?"

In the end, it doesn't make a bit of difference.

You need to evaluate fat burning over the course of days - not hour to hour basis - to gain a meaningful perspective on its impact on body comp.

CAlorie after burn

I’ve had a client once wear a Heart Rate monitor during a training session in which she only burned 350 calories. I had to explain to her that your body kept on burning calories for up to 48 hours post HIIT training!

True, the research does show that fasted cardio can increase fat utilisation during exercise compared to performing cardio in the fed state. Except this only occurs at very low levels of training intensity.

During moderate-to-high intensity levels, the body continues to break down a lot more fat when fasted compared to after you've eaten.

So far, so good.

But the rate of breakdown exceeds your body's ability to use the extra fatty acids for fuel. In other words, you have a lot of extra fatty acids floating around in the blood that can't be used by working muscles.

Ultimately, these fatty acids are repackaged into triglycerides post-workout, and then shuttled back into fat cells. So you've gone to excessive lengths… Only to wind up at the same place.

During moderate-to-high intensity levels, the body continues to break down a lot  more fat when fasted compared to after you've eaten.

Rack of weights

Fasted Cardio Doesn't Mean Skinny Minnie

Okay, so perhaps you're thinking that you'll just perform fasted low-intensity cardio to burn those few extra fat calories. Nice try, numpty. You see, training status also has an effect on the fasted cardio strategy.

Namely, if you exercise on a regular basis - the benefits of fasted cardio on fat utilisation are negligible even at low levels of intensity.

Horowitz's chart

Horowitz and colleagues found that when trained subjects exercised at 50% of their maximum heart rate an intensity that equates to a slow walk, there was no difference in the amount of fat burned -regardless of whether the subjects had eaten.

These results held true for the first 90 minutes of exercise; only after this period did fasted cardio begin producing a favourable shift in the amount of fat burned.

So unless you're willing, and able, to slave away on the treadmill for a couple of hours or more, fasted cardio provides no additional fat-burning benefits, irrespective of training intensity.

Fasted cardio makes even less sense when you take into account the impact of excess post-exercise oxygen consumption. EPOC, commonly referred to as the "afterburn," represents the number of calories expended after training.

Guess what? Eating before exercise promotes substantial increases in EPOC.

And guess where the vast majority of calories expended in the post-exercise period come from? You got it - fat!


"More epoc equals more fat burned. This favors eating prior to performing cardio."

There's also the intensity factor to consider. Research indicates that high-intensity interval training is more effective than steady-state cardio for fat loss.

Ever try to engage in HIIT session on an empty stomach? Bet you will go down like sack of spuds pretty quick!  In order to perform at a high level, your body needs a ready source of glycogen; deplete those stores and say goodbye to elevated training intensity.

HIIT while hungry

The net result is that fewer calories are burned both during and after exercise, thereby diminishing total fat loss.

On top of everything, fasted cardio can have a catabolic effect on muscle. Studies show that training in a glycogen-depleted state substantially increases the amount of tissue proteins burned for energy during exercise.

Protein losses can exceed 10 percent of the total calories burned over the course of a one-hour cardio session - more than double that of training in the fed state. Plus early morning training your cortisol levels are the highest so you put extra stress on your body by doing cardio.

To Cardio or Not to Cardio Before Breakfast


Summing up, the strategy to perform cardio on an empty stomach is misguided, particularly for physique athletes.

At best, the effects on body composition won't be any better than if you trained in a fed state; at worst, you'll lose muscle and reduce total fat loss.

So if you should eat… What should you eat prior to cardio?

The answer depends on several factors, including the duration and intensity of training, the timing of previous meals before the cardio session, and individual genetics.

But try taking 5 grams of Amino Acids before a training session on an empty stomach and refuel an hour after with a high quality protein and sweet potato from Muscle Food!

And as always hydrate and drink 1 litre of water per 50lbs of bodyweight a day.

Jamie Lloyd

About Jamie

Jamie Lloyd is an award winning Fit Pro, international best-selling author and fitness writer based in SW London.

He can be contacted on for personal training, group fitness training and nutrition coaching

Alternatively, you can connect with Jamie via his Social Media Channels – Facebook, Twitter and Instagram.



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