Calorie expenditure is not completely dependent on exercise. Metabolism is an involuntary activity that affects an individual's ability to burn calories.
BY CHRISTOPHER THEBERGE AND JOSEPH CANNON
When you are awake and resting, calories are burned just to keep you alive; this is considered your Resting Energy Expenditure (REE).
The REE between men and women is significantly different. A woman's metabolism is 10-15 percent slower than a man's because males naturally have more muscle mass, while females have a greater proportion of body fat.
In addition, hormone activity, like the hormones produced by the thyroid gland, establish overall metabolic rate. Body composition, unlike genetics, can be altered to some extent.
Body composition and metabolism
REE naturally decreases with age because of muscle mass loss. As a result, weight loss at a younger age is easier to accomplish. In general, losing body weight from fat or muscle lowers daily REE. It should be noted that at rest fat burns approximately 1-2 calories per hour versus muscle, which burns about 30-35 calories per hour. Therefore, maintaining body weight while decreasing fat and increasing muscle will raise REE greatly.
Environment and metabolism
The last and most modifiable factor for REE is environment. Certain stimulants can elicit a response in metabolism. Two of these that are used on a day-to-day basis are caffeine and nicotine. It has been reported in studies that two to three cups of coffee can raise REE as much as 12 percent. Cigarettes, which contain nicotine, also stimulate metabolism. People who smoke cigarettes often experience a weight gain after quitting. This may be due to a decrease in REE, as well as increased caloric consumption.
Temperature is another major environmental factor affecting metabolism. In cold environments, the combination of releasing certain hormones (i.e. adrenaline) and shivering can increase REE up to 400 percent. REE is raised in warmer environments due to increased cardiovascular activity and sweating.
Physical activity and metabolism
As you can see from the examples above, your metabolic rate is regulated by a number of factors. Exercise, in general, will increase your metabolic rate. When you exercise your body releases stored fuels to aid in energy production. Remember, your body composition greatly affects how many calories you burn in a typical day. Therefore, the more muscle mass you have, the more calories you will burn because muscle is metabolically active. Resistance exercise is the best way to increase muscle mass, while aerobic activity is better to increase your circulatory system and strengthen your heart.
However, exercising is just one part of the picture. In order to maintain a healthy body weight, you must match your energy intake with your energy output. (SOURCE: NAFWA)
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