Cardio
Almost as common a discussion as the weather, at least for UK people.
And like the weather we like to moan about it.
A lot.
Most likely if you’re a gym person you’ll be doing some form of it at some point of the year
and moaning about it
most likely on Facebook, with a picture of the digital read out showing how much you’ve suffered to earn your moan.
You know who you are 🙂
So aside from the sadists in the minority that love a bit of the C word, it can be said that most people agree that cardio of a duration longer than 5-10 minutes is not their favourite thing.
But we all do it.
Why? Well because we are weak people who like to stuff our faces from time to time and the fat piper has to be paid.
So how are you going to pay for your indulgence?
First of all are you going to do Fasted Cardio or Fed Cardio?
Then once you’ve either eaten or not or downed some BCAAs (get back to that later) is it going to be:
HIT (High Intensity Training) cardio or
LISS (Low Intensity Steady State) cardio ?
Since most of us doing cardio are not triathletes looking to increase our 5km performance, for most people the real question will be
‘Which burns the most fat the most and/or fastest?’
If you are into journal reading then you’re probably aware that there are a multitude of studies looking at the effect of fasted or non fasted cardio on fat loss.
If not then you ARE aware now.
What about FAT BURNING then?
Well if you’re in the fasted cardio camp then you may like Fasted cardio more fat oxidation 2016 where people burned more fat doing fasted cardio.
Great that settles it then. Fasted cardio is best.
However, a previous Study in ‘Metabolism’ showed no difference in total fat oxidation over 24 hours providing calories were matched in either fed or fasted conditions.
So
Same food eaten – Same calories burnt in cardio = Same fat burned over the day
Regardless of Fasted or Fed cardio
Also something relevant to gym goers Schoenfeld 2014 – Trained people, on a treadmill, doing an hours cardio. Sound familiar?
All subjects in a calorie deficit and either fasted or fed LISS cardio.
Results – they all lost weight in similar amounts
So its not exactly a slam dunk for the Fasted team. You could eat before training and still lose weight if you are eating less calories than you burn in a day
OK, back to fat ‘burning’
Yes that is correct that more fat is burned during fasted cardio but just because you oxidise more fat during exercise that doesn’t mean that
- you have burnt more fat over the course of the day
- you have burnt body fat
What does this crazy voodoo mean?
Surely you burn fat and that’s bloody fat isn’t it so I get shredz?
Unfortunately no.
Fat can be stored in the muscles as something called IMTAGs (Intra Muscular Triacylglycerides)
This is actually a good thing as it helps trained people to exercise for longer so its beneficial.
However if you’re a trained person then chances are when you burn fat during cardio, this is the fat you predominantly burn depending on the intensity.
Whats worse is that if you’re a regular gym goer then you’re probably more efficient at burning this fat in the muscle for your endurance cardio sessions.
Also the harder you Cardio the less FFA (bodyfat released fat energy) you burn in the workout.
From the graph you can see that actually going past 65% intensity (thats between a fast jog and a sprint) you actually burn LESS FAT in training.
This is why treadmills etc have a ‘FAT BURNING ZONE’ workout level at 65% of your intensity level.
So that 600 cals in 30 mins you just swore at on the stepper probably wasn’t all bodyfat.
Despite being fasted. WHY?
Because during exercise, blood flow is transferred to the muscles predominantly (80%) and even though you may release FFA (free fatty acids) from your bodyfat stores it may not be able to get to the muscles in vast quantities to be burnt as blood flow is diverted away from fat stores to a certain degree.
So in order to keep going for an hour the body may burn the fat in the IMTAGs first or at a higher percentage as its more efficient.
Even worse FFAs that are released from bodyfat during exercise may be redeposited as bodyfat if they are not used after being released.
More annoying is that the faster you go and more intense you workout the less likely you are to actually burn fat as fuel
So when you are smashing the stepper at 100 miles/steps/glutes an hour. That’s actually more carbs you are burning.
Which means all that extra effort you are making may actually be counterproductive to fat burning during the workout
However if you burn more calories in the workout regardless of carbs or fat used this is more calories used in the day. So this can be beneficial for fat loss over the 24 hour period.
So what about HIT vs LISS?
Remember
HIT is – Spin Classes, Interval Training, Prowler pushing, sled pulling, circuits etc which is short burst explosive all out bouts followed by a minute rest or so then repeat. This is done for 20-30 minutes
LISS is walking or jogging at a low speed on the treadmill, bike, stepper etc for 30-60 minutes normally
An older study in 1994 showed an interesting result in that in comparison HIT burnt more subcutaneous fat stores over time than LISS. This is often referenced in such discussions.
However another study on overweight people (which is lets face it the majority of the cardio doing population) showed that LISS not HIT was more beneficial for actual fat loss.
Then there’s the 2014 Study showing similar 24hr energy expenditure from HIT and LISS despite a lower time commitment that HIT requires.
So whats best?
Well lets look at some #science. 4 possible scenarios
Fasted HIT
HIT Training produces more Adrenaline (Ephinephrine) than LISS which activates an enzyme called HSL (Hormone Sensitive Lipase) which essentially is the ‘on’ switch for Lipolysis – breaking down of Fat Cells into Free Fatty Acids to be carried in the blood for fuel.
Consuming carbohydrates increases insulin which can suppress HSL leading to a reduction in lipolysis.
So Fasted HIT may be an option as this would produce maximum adrenaline and minimal insulin. Great for fat burning in a workout. However if you’ve ever tried HIT training then you’ll know doing it fasted is even worse an ordeal.
So you may not actually burn a lot of calories as you are hungry/tired or it seems harder than it is (This is called a higher RPE – rate of perceived exertion).
Also the kicker with HIT is that the actual ‘HIT’ part where you do stuff is glycolytic which means it uses muscle glycogen NOT fat. The fat use comes in the ‘resting’ bit between bouts where you recover, and also during something called EPOC which is that period after HIT where you are on the floor gasping for air despite finishing the exercise.
The EPOC period burns slightly more calories per minute than at normal rest. This can also be predominantly from fat as you are ‘at rest’.
Fed HIT
On the other hand if you eat before doing your HIT then the increased carbohydrate availability may boost your output to such a degree that you expend more calories albeit from glucose or muscle glycogen. So although you burn minimal fat in the workout you burn more calories as a total in the workout.
More calories burnt means a potentially higher calorie deficit in the day, which means as long as you don’t eat more to compensate then you may burn more bodyfat over 24 hours.
EPOC also applies to Fed HIT so there’s a potential benefit to this over LISS
Fasted LISS
Although the output of adrenaline is lower as intensity is lower you do LISS for longer meaning potentially more time for FFA to be released and then utilised by the body as fuel.
Because HIT is very short duration training if you do it right there’s less time for FFA to be used as fuel. Also due to its lower intensity the body can very easily use fat to fuel this activity although as discussed earlier that may be the IMTAGs not bodyfat.
Fed LISS
Seems the lazy option. Eat a nice meal then get on the treadmill/stepper etc and do a bit of low intensity exercise.
Right now I’m hearing you thinking ‘yeah thats lazy as hell, doesn’t hurt, no pain no gain’
HOWEVER
The Shimada study in 2013 showed that exercising after breakfast at 50% VO2 max (thats LISS) for 60 minutes oxidised more fat over 24 hours.
Now thats annoying for the 5am fasted cardio zealots. Get up, eat your brekkie then go and do a little easy LISS for an hour and burn more fat.
Just doesn’t seem right does it?
Bear in mind because of the food the subjects had more energy and burned more calories in the session so we are back to having maybe more mental motivation to do more which burns more calories total over the day.
So what is the ‘BEST’ cardio for fat burning?
The key thing to remember here is not to think about how much fat you can burn in the workout. The cards are stacked against you on that one.
- If you go fast then you burn more calories but not fat
- If you go slower then you may burn more fat but potentially from muscle fat not bodyfat
- If you go slow then you burn a low amount of calories, most likely from fat but not a lot
- If you do it fasted then you may burn more fat but may not be able to do as much plus if you go too fast you burn it from muscle fat stores and also potentially carbs
So instead think of the 24 hour picture, or indeed the 7 day picture. The ultimate determinant of bodyfat loss is calorie balance.
You need to burn more calories than you eat to lose bodyfat. This means using cardio as a tool to aid you.
The ultimate determining factor in if you lose bodyfat or not is always going to be if you are in a negative calorie balance.
- Cardio can help with the ‘burning’ as in you do more – Fed cardio can help this.
- Cardio can also help with the ‘eating less’ as doing cardio pre breakfast delays the first meal sometimes by an hour meaning you may eat less over the course of the day. – Fasted cardio can help with this
The actual answer for YOU may depend on firstly what type of person you are – trained or untrained, obese or not. Then how much time you have to do stuff.
Seeing as there’s no real difference over all the data on balance I would suggest that that the best type of cardio is one that best fits YOUR lifestyle
- If you like to do cardio first thing before breakfast. Then do that
- If you like to do HIT cardio and hate walking on a treadmill. Then do that
- If you want to smack back some BCAAs and bullet proof coffee pre LISS. Then do that
JUST DO IT and feel better for doing it. Just don’t feel superior than the other person doing another type
Getting up at 5am to do pre breakfast fasted cardio then selfie-ing it does not make you more of a ‘grinder’ or a ‘winner’ It actually probably makes you more of an annoyance to the social media crowd you’re trying to impress.
All about balance and how you weight the scales in YOUR life.
VERY IMPORTANT though. Don’t ‘reward yourself for being good’ and eat that biscuit or that extra bit of toast. Chances are this will result in ‘compensation’ by the body to make you eat enough to reset the calorie balance and take you out of the negative environment (fat burning) and undo all that good work you’ve done.
Some final parting thoughts.
(Morpheus Voice) What if I told you that while trying to shed fat you were actually shedding muscle?
This study – Lemon 1980 – Found that protein use for fuel increased dramatically during fasted training. (10% of the total calorie cost)
No problem you say? I’ll just bosh some BCAAs, protein loss sorted. Except, now its not fasted cardio.
Also, you’re still burning protein not fat.
Good News if you’re a women – you’re probably more likely to burn fat at a higher rate during exercise than your male counterpart Gender Study .
Bad News if you’re a woman you’re more likely to have a ‘craving for special foods’
Balance.
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