WHAT IS METABOLISM?
Metabolism as word or process can be defined in two simple statements. First, it is the chemical process within your body for the maintenance of life, yielding energy and forming substances necessary to life, such as blood, bone, muscle, fat, and so on. Second, it is the processing of specific substances, such as fat metabolism, iodine metabolism, and many others. While both of these relate to what we are talking about, the first statement is the important one for you at the moment. YOUR METABOLISM is how YOUR BODY goes about extracting energy from food, building and repairing tissue and organs, and how efficiently it does this. That last part about efficiency is a key point in weight loss and weight gain.
HOW IS METABOLISM RELATED TO WEIGHT LOSS...AND WEIGHT GAIN?
At various times in your life, your metabolism worked in different ways. Many of you can remember the days when you could eat anything you wanted and never gain a pound...a large pizza, three sodas with sugar, and some cinnamon sticks, and absolutely no change!
In the younger years of your life, your metabolism is in the high gears, probably the highest gears it will ever be in. For most of you in these years, weight gain and weight loss are not really issues. Some people, however, do have slower metabolic rates, and may have genetic tendencies or clinical conditions which cause them to have more of a weight gain than others of their age group. No matter which group you find yourself in, changing your metabolic rate, revving up your metabolism, will increase the speed and efficiency with which your body turns food into energy and body "parts and pieces".
Unfortunately, as you have long suspected, as you aged, your metabolism slowed down. Part of this is just something the body does with age, part of it, while somewhat related to age, is the effect of changes which take place in your way of life as you age. Fortunately, both are somewhat reversible, essentially through the same process. More on this in the last section. The part where your body just slows down has to do with "resting metabolism", and the other part...well, let's just call that "rusting metabolism".