| Metabolism is the sum of all physical and chemical processes by which living organized substance is produced and maintained, and the transformation by which energy is made available for the use of an organism.
Several of the hormones of the endocrine system are involved in controlling the rate and direction of metabolism. Thyroxine, a hormone produced and released by the thyroid gland, plays a key role in determining how fast or slow the chemical reactions of metabolism proceed in a person's body.
Another gland, the pancreas secretes hormones that help determine whether the body's main metabolic activity at a particular time will be anabolic or catabolic. For example, after eating a meal, usually more anabolic activity occurs because eating increases the level of glucose - the body's most important fuel - in the blood. The pancreas senses this increased level of glucose and releases the hormone insulin, that signals cells to increase their anabolic activities.
Well that isn't terribly helpful. Scientific explanations aren't what most of us need to understand things, and this is an ideal example. Let's try this another way.
Basal metabolism is what most of us are interested in. Basal metabolism is the amount of energy used for basic bodily functions. Breathing, temperature regulation, glandular activity, and even brain power require energy.
The latest "buzz phrase" in the diet and fitness world is "basal metabolic rate" or BMR. Your BMR is the rate at which you use up energy when you're resting or peaceful. A few key things to keep in mind:
- The more you weigh, the higher your BMR is.
- After the age of 20, your BMR drops about 2% per decade.
- The more muscular you are in proportion to body fat, the higher your BMR will be.
Calculating your BMR is all the rage these days. The easiest approach to calculate your approximate BMR is to divide your weight by 2 and multiply that by 24 to figure your minimum calorie requirements for a day of doing nothing. Example: 200 pounds divided by 2 is 100. 100 calories per hour x 24 hours per day is 2,400 calories per day. Of course, this is a rough estimation, but it gives you an idea of what your body needs every day.
A few closing thoughts about metabolism:
- The higher your metabolic rate, the faster you lose weight. Since muscle consumes more calories than fat, working out to build muscle and reduce fat will improve your BMR.
- Dieting causes your body to lower your BMR in response to the starvation it believes is occuring. Severe calorie restriction has a negative effect on fast weight loss since the body has slowed down its burning of calories. Keep this in mind when planning a calorie-restrictive diet.
- When you exercise, your BMR is increased for hours afterward.
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