What is really the importance of exercise for weight loss? You probably know that physical activity doesn't burn a humongous amount of calories, and paying close attention to your diet is a more productive way to get in shape.
Of course, this doesn't mean that you should cancel your gym membership. Exercise may not have a great impact on the amount of calories consumed but it can determine the composition of what is lost - fat or lean mass.
This shouldn't be a big secret if you have a minimal knowledge about fitness stuff. However, if the scale is your only concern, then forget about exercise for weight loss because it's not a good time investment for you.
During steady state aerobic exercise, caloric expenditure averages about 5 calories/minute at low intensities, increasing up to 10+ calories/minute as the intensity goes up.
What about interval training that is praised by so many fitness aficionados? Well, it burns pretty much the same amount of calories (because it alternates high/low intensity bouts), but may also cause overtraining when added to your regular workouts.
If you train vigorously for 30 minutes you burn about 300 calories, including your resting metabolic rate. But even without deducting your BMR, this energetic expense is so modest that maybe you should consider redesigning your diet instead of adding more exercise for weight loss.
For all this effort (going to gym, changing your clothes, warming up, cardio, traffic jam) you use up roughly the calories found in a small portion of french fries. Maybe you shouldn't go to McDonald's in the first place. Or if you go, at least skip the french fries.
You may argue that more energy is burned via the excess post-exercise oxygen consumption (EPOC), and you are partially right. It turns out that for Average Joe, the extra energy expended is about 20 calories, so it could make a difference if his plan is to get ripped in 15 years!
As a side note, EPOC is caused by an over-secretion in circulating hormones such as catecholamines – as well as other factors that are not important for our discussion.
It should be noted that steady state exercise stimulates slightly the noradrenaline release, but has no effect on adrenaline. For this reason, EPOC increases exponentially as a function of intensity and only linearly as a function of duration.
So if you intend to burn a decent amount of calories (over 100) while sitting on the couch and watching some retarded TV show, exercise has to be done not only at an increased intensity but also long enough to tax your energy homeostasis.
Interval training is too short to generate any reasonable EPOC effect, which is further diminished because most folks do the intervals in a way that doesn't have anything to do with high intensity exercise.
As it turns out, weight training (when is done properly) is the most effective way to perturb your body's homeostasis because skeletal muscles can be worked on a much larger scale. But even more energy is consumed via protein re-synthesis, which seems to be a costly process.
As a side note, many authors still falsely believe that the increased metabolic rate (caused by protein re-synthesis) is supposedly generated by more muscle tissue.
And some fitness gurus still claim that adding a few pounds of muscle will transform you in a fat burning furnace or other similar nonsense. (These myth propagators should get out of the '90s, and update their modest knowledge.)
Nevertheless, as I mentioned previously, the real value of exercise for weight loss is to keep or increase your lean muscle mass while being in a calorie deficit. In fact, your weight could remain the same or even slightly increase.
But it doesn't really matter as long as your body composition improves. You shouldn't be obsessed with your calorie expenditure or how much you weight if the mirror gives a good feedback.
Strength training combined with a slight calorie restriction causes a greater fat loss than just diet alone. Basically, a calorie deficit causes the fat loss and resistance training stimulates the body to keep its muscle tissue, so the result is that more fat has to be discarded.
From this perspective, aerobics and calorie restriction are essentially the same thing. This is not to say that this form of exercise is good-for-nothing if you know when and how to use it.
In fact, it could make a difference when you are already lean, and your goal is to get to lower digit body fat.
That's pretty much it about the importance of exercise for weight loss. So review your diet without getting lost in trivial details, and get serious about your training. Good luck!