Monday, October 27, 2008

The Caloric Balance

By Carl Juneau

How do you measure your caloric intake and output? Your caloric balance is the difference between your intake and expenditure of energy, or your output.

IN - OUT = BALANCE

Your Intake
As human beings, we consume food to produce energy. The amount of energy supplied by a given food is usually measured in calories (Cal). For example, a medium size apple contains 72 calories, a glass (250 mL) of 2% fat milk, 128, an egg (50 g), 78, and McDonald's Big Mac, 5632.

All the food you eat in a day is called the daily caloric intake (DCI). You can increase or decrease this number by eating more or less food. The average daily intake, in the US, was 2,618 calories for men and 1,877 calories for women in the year 1999-20003.

Your OUT
Your body spends the energy you get from eating in two ways: when you aren't doing anything and when you are doing something.

Resting metabolic rate The resting metabolic rate refers to the energy your body spends when you're awake but inactive in a fasted state at room temperature. It is, basically, the minimum amount of energy it needs to keep your cells alive. That includes tissue regeneration, regulation of the body's temperature, breathing, blood circulation and filtering, and hormonal and nervous activity. These functions are carried out by your liver, brain, heart, kidneys and muscles; these organs and tissues stay active, even when you're not. Thus, even when you're resting, you're spending calories big time. Actually, you might be surprised to learn that, for most people, the resting metabolic rate is the largest source of daily energy expenditure.

Physical activity Quite simply, you spend energy whenever you move. From your bed to the shower in the morning, from home to work or school, and so on. Even when you're sitting or standing, your muscles spend energy so you can maintain good posture. The amount of energy you spend that way in a day will depend on your lifestyle: some people are more sedentary like the office worker who travels by car and some are more active i.e. a manual worker, or someone who travels by foot or bike.

Sport and physical exercise also increase the amount of energy spent that way by a good margin. For example, a 121 pounds individual would spend roughly 75 calories per hour when sitting, 200 when shopping and about 450 when walking at a fast pace. Ultimately, physical activity can account for between 20 (complete sedentary lifestyle) and 50 % (athlete) of your daily caloric expense. The bottom line is: the more physically active you are, the more physical activity counts toward and increases your daily caloric expense.

Interestingly, exercise affects your OUT in two ways: first, it raises your daily output the days you are exercising. Second, in the long run and as you slowly build muscle, it increases your resting metabolic rate. The fact is that a pound of muscle is a lot more "active", from a metabolic perspective, than a pound of fat.

Muscle contracts when you move, as it is put to work when you exercise and
constantly rebuilds itself to keep at maximum ability for your daily movements. As we have seen, energy output can also be calculated in calories. Your daily caloric expense (DCE) is the sum of the energy required by your metabolism at rest in a day, plus the energy used to do other physical activity. - 15255

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