Two Hours of Daily Cardio: What Does It Do?

by Chris Shugart

The Study of Calories

What if we kept our diet the same but did a buncha cardio? Can we lose fat? How much? What about muscles? Check out this tutorial.

Simply put, choose one of these options to lose fat:

1. Eat fewer calories than your maintenance intake (dietary calorie deficit)
2. Consume or burn more calories (calorie deficit through exercise)
3. Eat less than care AND burn more calories with exercise

Yes, hormones, sleep, nutrient timing, and other factors play a role, but calories play a major role in any fat loss event.

Most of us choose number three when it comes to losing fat: we switch between “calories-in” and “calories-out.” But what would happen if we stuck to maintenance calories and found an energy deficit just by exercising? What if the workout was just cardio? And what if we found ourselves in a 1000-calorie deficit by doing two hours of daily cardio for 93 days?

Well, we probably wouldn’t! Fortunately, some researchers have done it, and there’s a lot we can learn from their crazy study.

Calories-Out Just Study

This lesson was crazy hard. The researchers recruited seven pairs of obese, identical conjoined twins to live in a research facility for several months. All meals were prepared for them and they were monitored by two researchers each time they ate to make sure they were consuming the correct number of calories required for the study.

During the initial evaluation, the 14 participants underwent every imaginable test to determine their maintenance regimen, including body weight, skin tone, blood work, biopsies…you name it.

Remember, the goal was to put them in a calorie deficit, not to cut calories. Their diet was not “food” – it was a diet of care and made for every young man. Macros were 50% carb, 15% protein, and 35% fat.

For exercise, participants rode a stationary bicycle (light to moderate) for a total of two hours per day: one exercise in the morning and one in the afternoon. The researchers made sure that everyone burns 1000 calories from exercise per day. They did this for 10 days in a row, with a day off, and repeated it several times. Made it to 93 days of being in a calorie deficit.

Are They Dead?

No. On average, they lost 11 kilograms without noticeable muscle loss. Some lost only 2 kilograms; some lost up to 17.5, but the average was 11.

What Can We Learn?

Cardio works. Sure, it has limitations and drawbacks, but it works despite all the influencers on social media saying, “Cardio doesn’t work!” Obviously, it is. Hey, I wish everyone would gain weight and lose muscle, so I would have an excuse to avoid cardio, but it never happened.

Based on CICO calculations (calories-in calories-out), the researchers expected to lose more fat. They ran the numbers and figured the average weight loss would be 14 pounds. So why only 11?

According to Dr. Bill Campbell, the topics of metabolisms probably changed as the study progressed. Like food, the body adapts to aerobic exercise. Sometimes this happens because “the body adapts to increased physical activity by reducing the energy used in other physical activities, especially non-exercise thermogenesis or NEAT,” Dr. Campbell says.

This is something that competitive bodybuilders realize: the more they increase their cardio, the less they want to move outside of the gym. In the case of this study, their 1000-calorie deficit may have turned into an 800-calorie deficit because they sat around at times, burning 200 fewer calories. Cardio still worked, but the calorie count changed. Your body, that sneaky guy, fights you like a ninja when you’re trying to lose fat.

Some of the subjects lost 2-3 kilograms while others lost 15-17. They all did the same exercise and ate the same diet. This reminds us not to compare our results with those of others. Although genetically identical twins had similar rates of fat loss, they were also not identical. For example, one twin lost 13 kilograms while his brother lost 9. Same exercise, same diet, same genes, but different results.

Calorie-out only fat loss plans can work. Eat what you normally eat and walk more. But it’s hard to do outside the lab.

I suspect most people don’t see fat loss because all they do is add cardio without being very conscious of what they eat. Cardio is good, but if they’ve been gaining weight slowly for years then they’re probably eating a lot of excess calories. The calories they burn through cardio only put them back on when they eat, but they keep their bodies overweight. (Try my 5/2 Protein diet if that’s you.)

Should I Do Two Hours of Cardio a Day?

No, but it helps a little. Dr. Campbell suggests a “sequential fat loss plan.” This is a fancy way of saying don’t fire all your fat loss bullets at once.

First, take care of the “calories-in” part of the equation: cut 300 to 500 calories a day by eating less. Your body will eventually adapt and slow down the rate of fat loss. NOW fire another bullet: add cardio as a new boost.

Although the people in this study were sedentary, people who lift muscles can be prone to muscle loss, so keep your protein high and lift regularly to prevent it. Shoot for one gram of protein per pound of body weight and use MD Protein (Buy on Amazon) making it easier to hit that number. As a bonus, MD Protein contains micellar casein, the only protein proven to be anti-catabolic.

References

1. C Bouchard, and others. “Response to intermittent high-intensity exercise in identical twins,” Obesity Research, 2013. DOI: 10.1002/j.1550-8528.1994.tb00087.
2. The Body Through Science, Dr. Bill Campbell. April, 2024, Issue 22.