Unpopular Opinion: Weight Training burns more fat than cardio.

I'm going to add the caveat as long as you are not in too steep of a calorie deficit* If you are in too big of a calorie deficit, you will lose some muscle regardless. Even professional body builders will lose a percentage of muscle mass during their cutting phase. They do everything they can to try and minimize the damage.... including using steroids. Also... cardio will burn muscle under the same situation as a calorie deficit.... create too big of a deficit, you're going to burn muscle.

"The body efficiently adapts to any given habitual level of cardio activity, slowing metabolic energy consumption to conserve it, the reason runners have slower heart beats and why it takes much greater duration and intensity of cardio activity for a seasoned athlete to burn the same calories as a deconditioned newbie doing the same thing."

No, not really, not by much. There's potentially some efficiency improvement with time when a person practices a specific type of cardio and increases skill, because the person wastes less energy doing the thing. How much calorie impact that has varies with the nature of the cardio, but it's not necessarily a large difference.

The main reason heart rate drops with training is that the heart gets stronger. When it's stronger, it pumps a higher blood volume per beat. Heart rate isn't directly correlated with calorie expenditure. Oxygen consumption is pretty well correlated with calorie expenditure, and blood carries the oxygen out to the body with each heartbeat. More blood volume per beat, more oxygen per beat.

Heart rate is a common proxy for oxygen consumption in calorie estimation, because there aren't good ways to measure oxygen consumption outside a sports lab. The work - in terms of force and distance as per physics - is the main determinant of energy (calories) required to do that work.

I've been doing the same type of cardio for around 24 years, much of that time in similar volumes. It still burns calories, and plenty of them. (Yep, my resting heart rate is lower now, and working at the same pace requires a lower heart rate than it used to. That's essentially the definition of cardiovascular improvement in fitness terms.) Perceived effort goes down, too, but that doesn't necessarily indicate significantly lower calorie expenditure, either.

Long-term high-level endurance athletes continue to have remarkably high calorie needs. We regular duffers don't need to worry about our bodies becoming so adapted to our cardio modality that we'll burn lots fewer calories. A few fewer? Maybe.

Yes, muscle burns more calories at rest than fat does, though both are metabolically active. Researchers vary in their estimates of that difference, but the estimates tend to be in the realm of 4-5 calories per pound per day. Since it takes weeks to add a pound of muscle even under ideal conditions, the numeric calorie benefit and the time scale to achieve it are both kind of underwhelming, IMO.

I do suspect being stronger - which happens faster than mass gain at first - may make it easier and more fun to move, so that people move more in daily life without much notiticing and burn more calories that way when stronger . . . but the same is true to some extent for improved cardiovascular fitness.

How those numbers work out is bound to be quite individual. As another factor, over-exercise for current fitness level will potentially cause calorie compensation/energy compensation - lower calorie expenditure in other parts of life - but that's pretty nuanced and situational, too.

Bodies are pretty complicated. "Strength training burns more fat than cardio" is IMO reductively simplistic.

For best health, longevity and quality of daily life, most people would be well-advised to do some of both strength exercise and cardio. During weight loss, it's ideal to do some strength exercise to at least preserve as much muscle mass as possible. Cardio will burn more calories per minute, which is helpful during weight loss so we can eat more and get better nutrition while losing weight at the sensibly moderate rate.

There are some studies suggesting that either cardio or strength exercise help persuade the body to keep muscle during a calorie deficit, with probably some edge to strength exercise. But a stupid-big calorie deficit is going to trigger muscle (or other lean tissue) loss, because there's only so much fat we can metabolize per day per pound of it we have on our bodies. Nutrition and sleep also affect body composition.

In the long run, I think what makes the biggest impact on permanent weight management is whatever exercise a person enjoys and will do consistently. That's a much bigger deal than which exercise is better in theory, because if we hate that perfect exercise, we'll procrastinate it when possible and probably drop it eventually. Exercise we don't do has zero benefits.

Also, speaking as if "cardio" is all one thing with the same impact on the body no matter the type of exercise . . . that's ridiculous. Different things - all of them called "cardio" - have different physical demands and therefore different effects on the body. Most of any muscle mass I have comes from so-called "cardio", and I do have more muscle mass than average for my demographic. I don't lift enough to account for it, I promise. 😆

It happens that my brother and I frequently discuss the relative merits of dieting, weightlifting, and "cardo." He being more of a weightlifter and I being more of an outdoor enthusiast.

My first observation is that using the term "cardo" to indicate any activity that drives your HR to Zone >3 pretty much indicates that you don't like to leave the gym: you'll be just as happy jumping rope in the corner as anything else. So have at it!

But, the various aerobic sports are completely different, and being trained well for one does not imply being trained well for another! Compare swimming, cycling, and running, for example. You have to train in each one separately to perform well in a triathlon.

I don't know whether cardio or resistance training is better for losing fat. I use, what I consider to be, reliable sources to get this type of information. In this case, I like this Institute of Human Anatomy video: How Your Body Really Burns Fat: Can We Control It?