When Too Much Cardio Is A Bad Thing

As humans we are wired to prefer the easy and safe route in anything we choose to do.

Would you rather hunt for your food or have it delivered to your door?

Would you rather take a cold shower or a warm shower?

Would you rather get up in front of an audience of 100 people and give a presentation or write it all down in an email and send it to them instead?

Most people are going to have their food delivered, take a warm shower, and write the email.

This instinctual drive to do the easy or safe thing isn’t a character flaw, instead it is a built in survival instinct. In general, if you stay away from danger you survive.

Hunting means potentially failing to kill anything and that means you could starve.

Being exposed to cold water for too long can mean death.

Failure in front of your peers (aka your tribe) could mean being kicked out of the tribe and that would mean a greater chance of death.

So when we decide to take up an exercise regimen we choose the modality we feel comfortable with, and for most people that is cardio.

Running, swimming, riding a bike are all things most of us have been doing since childhood. Doing a deadlift, a squat, a pull up, are very foreign for most. Not only that, but you have to go into a gym most of the time and do those exercises in front of other people. No one wants to embarrass themselves (remember, that fear of being kicked out of the tribe?).

As a result most people drift towards doing cardio and little else.

They run/bike/swim 3-7 times a week.

Now don’t get me wrong, is that better than doing nothing?


But too much of a good thing can also be bad for you, especially when implemented incorrectly. This is particularly true if your goal is fat loss.

What is wrong with doing too much cardio for fat loss?

A recent study outlines exactly what can go wrong [1].

In this study there were three groups, a control group which was only given healthy living advice but did no exercise, a low exercise group which received the same healthy living advice but was burning 800-1000 kcals/week via aerobic training sessions on the treadmill, and a high exercise group that again received the same healthy living advice but was doing 2000-2500 kcals/week via aerobic training sessions on the treadmill.

As you might predict, the high exercise group lost the most weight, losing about 2kg or 4.4 lbs of body fat over the course of 24 weeks. Surprisingly the low exercise group didn’t lose any fat, and this is important to keep in mind as you continue to read this blog post.

While 2kg of fat loss is certainly a good thing, if that is your goal, it is 50% of what researchers would have predicted based on their baseline energy intake and the expenditure predicted by the amount of exercise that occurred.

What happened?

When researchers compared how many calories the high dose exercisers were expending based on spending time in a metabolic chamber, they saw a ~4% decrease in expenditure.

Did these exercisers experience the dreaded “metabolic adaptation”?

Kind of, they were certainly expending less energy than prior to the exercise intervention, but it might not be as bad as you think.

First off they lost weight, that means by default they are going to be burning less calories. The more weight you carry the more calories you burn.

Second, researchers also observed a 2.3% decrease in energy expended outside of exercise. Basically they were moving less than they were before.

Those two things will account for the reduction in energy expenditure measured by the metabolic chamber.

However, there is one more thing that affected the deviation between actual weight loss and predicted weight loss, the high dose exercise group increased energy intake by 124kcals/day! The low dose exercise group also increased their energy intake by 91kcal/day, this is why the low dose exercise group did not see any weight loss.

So combined with the reduction in energy expenditure due to weight loss and less overall activity and the increase in calories consumed per day this is why high dose exercise group didn’t achieve the predicted weight loss.

The results of this study might shine a pretty bad light on cardio and its benefits for fat loss. However I don’t think this is as bad as it looks and the solution, in my opinion, to this problem is making sure you have some form of cognitive oversight over your food consumption as well as your overall activity.

What do I mean by “cognitive oversight”? Essentially that is a fancy term for tracking. Part of the “problem” the high exercise group faced in this study is that because they added so much more activity, they subconsciously decreased their activity outside of exercise while at the same time increasing their overall food intake.

This is natural, our bodies and brain are looking for the easier path forward that allows us to survive as we talked about above. Could you survive while keeping the same food intake and amount of movement while adding in all this exercise?

Probably, but that would be more difficult and risky

The high exercise group is in a negative energy state and if they keep this up they will run out of energy so the body subconsciously sends signals to move less and motivates you to consume more food in an effort to return you to energy balance.

To avoid these subconscious changes we can use cognitive oversight to make sure we don’t change our food intake and movement practices. This could look like tracking food via an app like Cronometer and using a step counter like a watch or it could just be as simple as making note of how you are eating and moving prior to starting your cardio routine and making sure it does not change. However you choose to implement the cognitive oversight over your food and movement the goal is to make sure they do not change from baseline, just choose an approach that works for you.

The other thing that I would do differently than this study is to add in some strength training and not only do cardio.

Burning 2000-2500 kcals/week through cardio is not a huge amount depending on where you are starting from. Considering that average participant in the high exercise group weighted around 200lbs and they were running aerobically they would be burning around 1000 kcals/hour running 10 minute miles. They can reach the 2000 kcals/week from the study in just 2 hours of running a week at that weight and pace. That’s six 20 minute runs a week. While that is more exercise than 75 minutes of vigorous exercise the WHO recommends a week, it’s very little when compared to someone training for any kind of endurance event.

My point is that even the high exercise group could afford to squeeze in 1-2 strength training sessions in their routine, even if they had to cut 1-2 days of cardio out to do it. That would go a long way in combating the subconscious decrease in movement and increase in calories because they would be running less and burning fewer calories overall while at the same time sending the signal to build lean muscle. Not only would these participants see the same rate of fat loss or maybe even more fat loss, they would at least maintain muscle or even gain muscle.

Doing cardio is not necessarily bad if your goal is fat loss, but doing cardio without monitoring food intake and movement outside of exercise can lead to minimal results as we see in the high exercise group or no results as we see in the low exercise group because our bodies are designed to take the easy and safest approach possible. This is a design benefit ancestrally but can work against us in today’s modern world of food abundance.

While I normally talk about correcting ancestral mismatches, in this case we are trying to work against our ancestral norm of defaulting to the easier and safest approach. That is OK, as long as you do it in a sustainable way. That means being mindful of your food intake, your movement and the other signals your body is sending you. If your sleep starts to suffer, your mood turns sour, your hunger is out of control, your body temperature regulation is off, well it might be a sign that you are doing too much cardio and eating too little and you need to back off a bit and get back to the ancestral norm. Each week I try to convey information like this via blogs, emails, and videos that I send out to my newsletter. If you like what you have learned here, sign up for my newsletter below to continue to get more information just like this delivered to your inbox on a weekly basis.

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  1. (2021, May 4). Effect of Aerobic Exercise-induced Weight Loss on the Components …. Retrieved July 3, 2021, from https://www.researchgate.net/publication/351246814_Effect_of_Aerobic_Exercise-induced_Weight_Loss_on_the_Components_of_Daily_Energy_Expenditure

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