I want to start by saying I’m not against doing cardio, because it does of course have plenty of benefits. That being said, it just isn’t the most efficient way to burn fat.
In business, you can either trade your time for money or you can create passive revenue streams that keep paying you whether you’re on the clock or not. The exact same principle applies to burning calories. Cardio is essentially the equivalent of getting paid for your time and starting over at the end of each day. Building muscle, however, is the best passive revenue stream available for burning body fat. Did you know that every pound of muscle tissue burns an average of 50 calories per day, regardless of physical activity? Yep, even if you sit on the couch all day (but please don’t!).
Muscle isn’t the only factor when it comes to your metabolism, but it’s easily the one that you can reliably assert the most control over. Building muscle cranks up the dial on your metabolic thermostat so you can become a fat burning machine, even on your off days. Let’s say you do a cardio session every day for an hour and burn 500 calories. If you were to build 10 pounds of muscle, you would burn about 500 additional calories every single day without that cardio session (and of course even more if you still did the cardio). Not to mention, if you didn’t do the hour of cardio, you would have still burned some calories. If you would have burned 80 calories even if you skipped the cardio, then the net benefit is really only 420 calories and comes up short of the 10 pounds of muscle.
If you want to take it even further, you could work to put on 20 pounds of muscle and add 1000 calories / day to your metabolism instead! These may sound like astronomical numbers, but 5lbs of muscle is far more compact than 5lbs of fat. Five pounds of muscle is about the size of a fist (see picture above), so adding as little as 10 pounds of muscle spread throughout your whole body is not going to suddenly make you bulky if that’s not what you’re going for.
Let’s say you want to build muscle, but you also want to keep doing cardio for other health reasons (heart & lung health, stress relief, etc.), but you don’t have time to fit in both cardio and strength training to build muscle. One possible solution is to do circuit style strength training so that you can build muscle while keeping your heart rate up at the same time, thus covering both bases in half the time. If you’re not familiar with the idea of circuit training, it’s basically just performing your resistance exercises in a rotation so that you perform one round of multiple exercises before returning again to the first exercise – this allows you to keep moving rather than just waiting between sets until you’re ready to perform the same exercise again. There are of course other advantages and disadvantages to both approaches, but that’s a subject for another post.
Whether your direct goal is to gain muscle or not, never forget the importance of muscle in regulating your metabolism. If you want to optimize your fat-burning and get leaner, stop ignoring resistance training to fit in more cardio.