I went to a Jazzercise class last week with some friends. Jazzercise is basically aerobics, but each song has its own choreography. It was a lot of fun, and quite similar to what I used to do as an aerobics instructor. But it was interesting listening to them, and doing all this cardio when... I don't believe in it.
Let me just say first of all, that moving your body is good. Doing jazzercise, or aerobics, or jogging does keep your heart pumping and makes you feel good. But for weight loss (the reason most people exercise), I believe cardio is the least effective form of exercise.
Here are the reasons why I no longer believe in cardio:
It's not as simple as "calories in, calories out." The instructors at my class today reminded us of how many calories we were burning. ("One class can burn up to 600 calories, ladies!") But scientific studies have shown that cardiovascular exercise makes you hungrier. Your body wants to replace those lost calories. Basically, with cardio, you are fighting your body to lose weight. Dr. Stephan Guyenet uses a great analogy that helped me to visualize this. (You can listen to the entire podcast here.) He said that losing weight by doing cardio is like having the a/c on in your house. But when it gets too cool and you want to warm it up a bit, you open the front door. Well, you know what happens then, right? The air conditioner works hard to cool the house, requiring more energy. With cardio, you are burning more calories (working harder), so your body will crave more calories for energy too.
If "calories in, calories out" worked, then you would exercise (calories out) and eat less (calories in). But that is missing one very simple physiological process: hunger. You can only fight your body's hunger signals for so long.
Cardio can do harm to joints and cause overuse injuries. During the weight portion of the class, we worked very specific small muscle groups over and over and over. Jumping and running definitely have their place in an exercise regimen, but all you have to do is look at the number of runners with bad knees to know that overuse injuries occur. Often.
Your body adapts to cardio. This means that doing the same exercise becomes less effective over time. Your body adapts to the exercise-- that's why it gets easier. Your body is becoming more efficient at the exercise. Good for the body, but bad for weight loss. That means that to do exactly the same exercise, you will be burning less calories after a month than you were when you started.
So maybe you know someone who started doing cardiovascular exercise and lost a lot of weight. Maybe you know a lot of people who have done that. But what if it wasn't the exercise at all? What if, like my instructor said today, "after I've done a class, I don't want to go eat that cheeseburger. I worked so hard to burn those calories, I don't want to put them back in." Maybe cardio exercise changes our psyche more than our figure, causing us to make other changes, like in what we eat. Or maybe, when we start working out, we are burning so many calories that our body has a hard time replacing them all through food. But as time goes on, and our bodies adapt, we burn less calories and our exercise is less effective at helping us lose weight.
Coming up: In my next post I will detail what I believe in instead of cardio and how to work with your body to lose weight.