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How Does 'Cardio' Reduce Bodyfat?


Key word: how

Lay people tend to treat cardio as a means by which to burn calories. But if this is how cardio reduces bodyfat, you could just eat less calories. I suspect 'cardio' might reduce bodyfat by using bodyfat to fuel the exercise. But if this is the 'how', it doesn't explain why so many people advocate exercise such as sprints for reducing bodyfat. Wouldn't such exercise utilise creatine and glycogen in the body?

NB. I realise nutrition is the most important aspect of getting lean. But if cardio also plays a role (even a small one) this question is directed at how it works.

Thanks for any info.






SS cardio uses primarily fats for energy.
Sprints use glucose, however create a greater EPOC than SS cardio.

Both ways can expend the same number of calories, however a lot of people want to do low-intensity cardio because more of the calories will come from fats.
Which I don't get because a deficit is a deficit, but whatever.


Thanks for your input.

If the only reason you are doing the cardio is to create a calorie deficit, wouldn't it be much easier to just eat less calories rather than to burn them through exercise?


people use different methods...

some people do zero cardio...some people do cardio twice a day....i heard of figure competitors doing 3 cardio sessions a day...

same thing with diet...some people do a keto diet to get lean some eat carbs...

it really depends on your strategy...I'm sure you could achieve results both ways but one way might be better for your as an individual...it's really trial and error and intensity of your efforts


Absolutely not.

The less you eat (read: food that physically goes in your mouth and through your body, not talking about net calorie balance) the slower your metabolism gets.

If you continuously and systematically lower your calories in an effort to lose fat you'll end up accomplishing a few things. These "things" are not good for body composition. You'll slow your metabolism making the whole process more arduous AND your body will think you are starving and will begin to burn muscle and store fat in an effort to save itself from this "perceived" threat.

The more you eat while still remaining in a caloric surplus the better chance you give your body to burn fat.

That's about as simple of an explanation as one can give. And after being a member on this site for 3 years you really should have these concepts drilled down. Honestly.

Did you think people simply enjoyed using the stepmill while trying to get to 3% bodyfat to win their BBing show?


What the hell does NB mean? I keep seeing it pop up around here.


Yah, because anorexics are super hot... last I checked they specialized in eating less calories.




You're going to burn fat in a caloric surplus?

OP, diet only to burn fat will only result in continuous plateaus, then you reducing your calories even lower than before which will screw up your metabolism. Your body is in constant survival mode, so if you feed it less, then your BMR will lower because it will "think" that it's starving and will aim to burn less calories just to function.


That makes sense. I have realised that part of my confusion has been due to me underestimating how many calories can be burned through exercise. My initial thought was that if cardio reeduced fat only through helping create a caloric deficit, it would be much easier to simply reduce caloric intake slightly. However, I now realise that to match the calories burned through exercise with not eating could actually involve a substantial reduction in calories which would not be beneficial for the reasons you have outlined.

If, however, cardio does only reduce bodyfat by helping you achieve a caloric deficit, why do people recommend you do it whilst bulking to 'keep fat levels in check'? If you are bulking you are still going to be eating a surplus of calories even with the cardio, so how does it keep bodyfat in check? Is it simply a matter of reducing your caloric surplus for that particular day, which may lead to less fat gain?


Think of it this way. Having a caloric deficit at 2000 calories allows your body only so much muscle preservation. Having a caloric deficit at 3500 calories allows your body to have a much higher rate of preserving muscle while still burning fat.

Yes you could reduce your caloric surplus for that particular day, and you also may miss out on growth by having a lower caloric restriction. Since building attributable size is much harder then burning fat, it's better from an aesthetic and usually athletic standpoint to have the fat gain with the higher rate of muscle gain.

There's a reason the idiots out there that stay the same size year after year by not eating enough thinking that they are going to "lean bulk" never actually put on much size.

Think of your body as an engine. Eating at 2k calories to cut and not doing cardio lets you travel at 50 mph. Eating at 4k calories to cut and doing cardio to induce a caloric deficit allows you to travel at 100 mph.


Thanks, this really summed it up quite well for me. I've only been on here a short while and although I have seen you smash some fools mercilessly I usually find what you say very constructive and helpful.


One more thing. A lot of people suggest doing cardio first thing in the morning on an empty stomach. I assumed the reasoning was to utilise stored fat rather than glycogen, but if its just about calories, why would it matter?

None of this is that important to me - I'm just curious. Though I've been training for a while, I've never really done any cardio. I started at 127lbs, so losing weight was never one of my goals!


I don't think anyone here has said it's just about calories. Have you seriously not read anything on this site? Go read all the articles....they're a wealth of information, and it's all free information.


I'm not suggesting losing fat is just about calories, but that the responses indicate that cardio is just about calories. Specifically, placing the body in a caloric deficit whilst still consuming sufficient amounts of food and nutrients.


'Please note'


Calories are fuel for cardio. You are completely over-complicating this. As said, you CAN place yourself in a caloric deficit with zero cardio, simply by nutritional means. Annorexics do it daily. As bonez and others have outlined above, while doing this for short periods of time can be "okay" extended periods of this can result in a myriad of issues.


I understand and accept this. As noted, I think my initial confusion was caused by underestimating the amount of calories burned through exercise.

My second question was as to how this understanding fits in with such strategies as fasted cardio.

I don't agree that I'm overcomplicating anything. I was merely inquiring into the process through which cardio burns fat. It's more curiosity than anything else. Although, now that I have gained a considerable amount of size, I will be contemplating introducing cardio into my training regime probably within the next 6 months or so.

Thanks for your input.