Does Cardio Make You Fat?

In a recent article, titled “Does Cardio Make You Fat? Study says yes”, the author claimed that cardio makes you fat. And if you’ve heard any of my public speaking engagements, I frequently say that “excessive and exclusive cardio makes you fat.” Those are the big qualifiers: excessive and exclusive.

Original source: here.

            So a lot of the points made by the author of the article are very valid, and I agree with many of them. To briefly summarize, the author stated:

• The fat burning zone is taken out of context.
• If you burn a lot of fat during a workout (which is what cardio does), your store more fat outside your workout.
• The primary thyroid hormone, T3 is suppressed. This is the hormone that regulates your metabolism.
• The fitter you get, the fewer calories you burn.
• Cardio stimulates the appetite, and forces you to eat more than you burned
• Cardio burns muscle, which slows down the metabolism

All these points, I agree with, and have stated myself during public speaking engagements. But again, the qualifier is excessive and exclusive.

I frequently get invited to speak at Running Rooms, so I get to work with a lot of runners. So from first-hand experience, I can tell you that a lot of people who run half marathons and marathons are 20+ pounds overweight. No question there.

So then, an intelligent reader on facebook asked these questions:

1. Is an increase in cortisol (as a result of cardio training) a bad thing? And with regular training, shouldn’t the cortisol response increase as the body adapts to stress?
2. Scarring of the heart tissue: isn’t the heart strengthened from cardio as a result of the stress placed on the heart’s chambers (increased blood flow, heart rate, stroke volume, blood pressure)?
3. Jolting stress on the joints: wasn’t that claim also made about lifting heavy, squatting too low and running with vibrams? What about swimming or the various machines designed to ease joint strain? What about super marathon runners who run without shoes? 

Does cardio have its place in the future of training? Thoughts? 

Let’s address these questions one-by-one:

1. Is an increase in cortisol (as a result of cardio training) a bad thing? And with regular training, shouldn’t the cortisol response increase as the body adapts to stress?

No, an increase in cortisol is not a bad thing. In fact, it’s a very desirable thing. Cortisol has several benefits as they pertain to endurance exercise:

• It’s a glucocorticoid hormone. That means that it raises blood sugar. That’s good. We need blood sugar to be higher during endurance exercise, to make it readily accessible to the muscle cells that need it.
• It increases your energy.
• It’s an anti-inflammatory. Almost all exercise creates inflammation in the body. Cortisol helps reduce that.

However, elevated cortisol as a result of endurance training does become a bad thing in a person who walks around with chronically elevated, or chronically depressed cortisol. In a healthy person, cortisol should rise during endurance training, and promptly come back down to baseline once endurance training is over with. Unfortunately many people taking on endurance training have pre-existing cortisol imbalances to begin with. And doing endurance training isn’t helping.

I don’t have specific data on how cortisol adapts to training, but my thinking is that over time, a stress becomes less stressful. So a person would secrete less cortisol, not more. But of course, I could be wrong on this one.

1. Scarring of the heart tissue: isn’t the heart strengthened from cardio as a result of the stress placed on the heart’s chambers (increased blood flow, heart rate, stroke volume, blood pressure)?

Yes, the heart is strengthened. But no reason why it can’t be scarred as well. Both happen at the same time. Think of strength training. Squats strengthen the legs. But they also create scar tissue in the legs. Just a by-product of getting stronger. Any microtrauma will create both increased strength, as well as scarring.

1. Jolting stress on the joints: wasn’t that claim also made about lifting heavy, squatting too low and running with vibrams? What about swimming or the various machines designed to ease joint strain? What about super marathon runners who run without shoes?

There’s no argument that lifting heavy and squatting too low (with weight) will absolutely damage the joints. Ask most powerlifters that have been lifting for 20+ years. Their joints are beat up. Regardless of what supplements they take for their joints, they always say they “feel it.” Squatting low without weight is not a problem, and in many countries in the world, the deep squat is their resting position.

So yes, heavy weights over many years can be problem on the joints. And so can running. With heavy weights, you do very few repetitions (compared to running), but you do use high weights. With running, the weight you use is fairly light. But you do A LOT of repetitions. For example, if each step you take is 1 metre, in a 5K run, you’ve taken 2500 steps per leg. That’s a lot of repetitions.

Swimming does tend to be easier on the joints because of the decrease compression, and that’s why it’s frequently recommended for those with arthritis.

Super marathon runners are a different breed. The article talks about the recreational runner. Super marathon runners are professionals. And at the elite level, they had the typical ultra marathoner body and joint structure before they ever were super marathoners. This is a case when a great athlete is born, not made. Through training, you can increase your endurance, you can increase your stroke volume, and decrease your heart rate. But no amount of training will change you bone and joint structure.