s composed of water, adipose tissue (better known as fat) and lean tissue, which is everything else (muscle, bone, hair, and other tissues).

Your muscle mass is an important part of your lean tissue. In fact a majority of your body's machinery is composed of muscle, including many of your internal organs. The tiny engines of muscle cells are "metabolically active" because they require energy to perform their work. Muscles help you breathe, digest food,

The word metabolism is thrown around a lot these days. Some people complain about having a "slow" or sluggish metabolism or buy products that claim to "boost" their metabolism. But what is metabolism anyway?

In a nutshell, metabolism simply refers to the amount of fuel or energy that your body burns each day. While images of treadmills and aerobics classes may come to mind, you’re using energy right now just reading this article.

The largest part of your metabolism, called basal metabolism, is the amount of fuel your body burns to support your basic bodily functions. These vital functions include your heartbeat, breathing, brain function and numerous other important, but invisible, activities going on inside of you at all times. Even eating, digesting and processing food contribute to your metabolism.

In fact, every little cell in your body is like a tiny engine that burns fuel continuously in the process of doing its job. These tiny engines never shut off while you are alive. Even when you’re sleeping or sitting still, your body's cells are still actively working. It's just like a car; when the engine is running, it's burning fuel—even if it's just sitting in the driveway.

Your activity level is another significant part of your fuel needs. On top of your basal metabolism, your body's workload increases with any type of activity, from brushing your teeth and taking a shower, to walking around your home, school or office.

This extra work increases the number of calories the cells burn, because the "labor" of the cells has increased. For instance, your lung cells must work to take in oxygen and release carbon dioxide, but they work harder when you're walking at a brisk pace than when you're sitting in a chair.

Another piece to this metabolic puzzle is your body composition. Your body is composed of water, adipose tissue (better known as fat) and lean tissue, which is everything else (muscle, bone, hair, and other tissues).

Your muscle mass is an important part of your lean tissue. In fact a majority of your body's machinery is composed of muscle, including many of your internal organs. The tiny engines of muscle cells are "metabolically active" because they require energy to perform their work. Muscles help you breathe, digest food,

of your metabolism, called basal metabolism, is the amount of fuel your body burns to support your basic bodily functions. These vital functions include your heartbeat, breathing, brain function and numerous other important, but invisible, activities going on inside of you at all times. Even eating, digesting and processing food contribute to your metabolism.

In fact, every little cell in your body is like a tiny engine that burns fuel continuously in the process of doing its job. These tiny engines never shut off while you are alive. Even when you’re sleeping or sitting still, your body's cells are still actively working. It's just like a car; when the engine is running, it's burning fuel—even if it's just sitting in the driveway.

Your activity level is another significant part of your fuel needs. On top of your basal metabolism, your body's workload increases with any type of activity, from brushing your teeth and taking a shower, to walking around your home, school or office.

This extra work increases the number of calories the cells burn, because the "labor" of the cells has increased. For instance, your lung cells must work to take in oxygen and release carbon dioxide, but they work harder when you're walking at a brisk pace than when you're sitting in a chair.

Another piece to this metabolic puzzle is your body composition. Your body is composed of water, adipose tissue (better known as fat) and lean tissue, which is everything else (muscle, bone, hair, and other tissues).

Your muscle mass is an important part of your lean tissue. In fact a majority of your body's machinery is composed of muscle, including many of your internal organs. The tiny engines of muscle cells are "metabolically active" because they require energy to perform their work. Muscles help you breathe, digest food,

the process of doing its job. These tiny engines never shut off while you are alive. Even when you’re sleeping or sitting still, your body's cells are still actively working. It's just like a car; when the engine is running, it's burning fuel—even if it's just sitting in the driveway.

Your activity level is another significant part of your fuel needs. On top of your basal metabolism, your body's workload increases with any type of activity, from brushing your teeth and taking a shower, to walking around your home, school or office.

This extra work increases the number of calories the cells burn, because the "labor" of the cells has increased. For instance, your lung cells must work to take in oxygen and release carbon dioxide, but they work harder when you're walking at a brisk pace than when you're sitting in a chair.

Another piece to this metabolic puzzle is your body composition. Your body is composed of water, adipose tissue (better known as fat) and lean tissue, which is everything else (muscle, bone, hair, and other tissues).

Your muscle mass is an important part of your lean tissue. In fact a majority of your body's machinery is composed of muscle, including many of your internal organs. The tiny engines of muscle cells are "metabolically active" because they require energy to perform their work. Muscles help you breathe, digest food,

ng your teeth and taking a shower, to walking around your home, school or office.

This extra work increases the number of calories the cells burn, because the "labor" of the cells has increased. For instance, your lung cells must work to take in oxygen and release carbon dioxide, but they work harder when you're walking at a brisk pace than when you're sitting in a chair.

Another piece to this metabolic puzzle is your body composition. Your body is composed of water, adipose tissue (better known as fat) and lean tissue, which is everything else (muscle, bone, hair, and other tissues).

Your muscle mass is an important part of your lean tissue. In fact a majority of your body's machinery is composed of muscle, including many of your internal organs. The tiny engines of muscle cells are "metabolically active" because they require energy to perform their work. Muscles help you breathe, digest food,

s composed of water, adipose tissue (better known as fat) and lean tissue, which is everything else (muscle, bone, hair, and other tissues).

Your muscle mass is an important part of your lean tissue. In fact a majority of your body's machinery is composed of muscle, including many of your internal organs. The tiny engines of muscle cells are "metabolically active" because they require energy to perform their work. Muscles help you breathe, digest food, move your body, lift and carry objects and even stand upright.

Not only do muscle cells require more energy to do their work, but it also takes energy to build and maintain them. Whenever you do a little more than your body is accustomed to, your body will build more muscle to accommodate the new workload. Building this new muscle tissue requires more fuel. It's like a factory; as the number of workers increases, the productivity or output goes up.

There is another significant part of metabolism—food. To your body, food is the fuel that keeps this process running smoothly. Your cells must have an energy supply in order to perform their required tasks. Without an adequate amount of fuel, your cells cannot function properly, resulting in unfavorable consequences.

Think about your car again. If it runs out of gasoline, it will putter and stop. However, in order to stay alive, your body's cells cannot all just shut off. When your cells are low on fuel from food, your body will turn to its "reserve tanks" to utilize other energy sources. Initially, it will use up carbohydrate that has been stored as glycogen in your muscles and liver. When that is gone, it will begin to break down certain tissues to use for its energy supply, specifically, fat and muscle.

In a state of ongoing fuel shortage or semi-starvation, your body must pick and choose which cells to continue supporting and which ones to "drop." A priority list is developed, and needless to say, the cells that provide vital activities take top priority. Remember, muscle cells require a lot of energy, so those that aren’t being used regularly will be given the pink slip!

When your food supply remains low, your cells must also become more efficient. That is, they attempt to perform their jobs without burning as many calories; they adapt to t