Today we are going to talk about the science behind losing weight, specifically we are going to talk about ‘metabolism’. I am going to try to keep the discussion on a level that we can all understand. I do not speak ‘Science’ well, though I do understand the language. I am better at speaking English.
What is metabolism?
Metabolism is a result of cellular activity. Our bodies are made of millions of cells. These cells eat sugar, fat and/or protein and generate energy. The more our cells eat, the more energy they create. Our goal in losing weight is to increase the metabolism of as many of the cells in our body as we can, thereby increasing our caloric burn (which means, losing weight). The more cells we get burning calories = the greater our total body metabolism = the greater our success in losing weight.
If metabolism means burning sugar and fat, is there a way we can increase our metabolism so we burn more sugar and more fat?
Our bodies have a ‘resting metabolism’ where we burn a certain amount of calories when we are simply sitting and doing nothing. When we exercise we burn calories. The more vigorous or intensely we exercise, the more calories we burn. Also important, the more intensely we exercise, the more muscle mass we develop. Because muscle tissue burns so much fuel, increased muscle mass, means greater metabolic burn. So, yes, we can increase our resting metabolism by increasing our muscular development.
Why is 45 minutes or longer such a big deal when it comes to losing weight?
As stated above, the more intense the exercise session, the greater the increase in metabolism. The greater the increase in metabolism, the more successful you will be in losing weight. Intensity of exercise can be measured by how hard you are working out and by how long you are working out. Short periods of exercise (especially short periods of low level exercise) simply do not do enough to be effective in losing weight.
Is higher intensity exercise more effective than lower intensity exercise? Or, to put it another way, is running more effective at losing weight than walking? Is sprinting more effective than jogging?
Yes. Sprinting vigorously uses more muscles groups and develops more muscle mass than jogging or walking does. Compare the body types of an experienced sprinter with an experienced distance runner and it will immediately be noted that the sprinter has a nicely developed upper body muscle mass, while the upper body of a distance runner is somewhat atrophied. This is not to imply that distance running is not an effective form of weight loss. It is effective, just less so than high intensity sprinting.
Is there is some scientific debate on whether or not walking fast or running slow (jogging) burns about the same amount of calories?
The definition of running is that at some point in every stride both feet are off the ground. That means every running step results in a small ‘jump’ off of the ground. This process of small jumps burns more calories than walking simply because walking does not need extra calories to escape gravity every step. It might be that the calorie burn of fast walking versus slow running is about the same, but without a doubt running will burn more calories than walking.
Sprinting, and high intensity exercise in general, burns even more calories. In a slow run (jog), the runner’s upper body is relaxed. The upper body is not doing much, so there is very little calorie burn occuring in these muscles. A sprinter is driving their arms and strongly contracting their trunk muscles. This extra motor activity results in extra calorie burn. Even better, because sprinting (or high intensity exercise) gives the upper body muscles such a good workout, the result is better development of the upper body muscles – so it follows that the resting metabolism of a sprinter is higher than the resting metabolism of a distance runner.
Are you saying that we should ‘sprint’ instead of ‘jog’?
Nope. I am saying that if you want to lose weight you should exercise for 45 minutes a day or more. The higher the intensity of your workout, the easier it will be to lose weight, but that is not what is most important. What is most important is that you should find an exercise that you like doing for 45 minutes a day or longer… and then do it.
Editor’s note: This is an article that was published under ‘Workout Journal’, though it could have been published under ‘Ask the PT’, as it responds to a conversation I had with a reader.