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 The human body spends the energy drawn from food in basically two ways: to fuel the metabolism at rest and for physical activity.

Resting metabolic rate

The resting metabolic rate refers to the energy your body spends when you're not doing anything that requires any physical effort, such as sitting or sleeping. It just uses enough energy to keep your body's vital functions 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 work all the time, even when you're not. Thus, when you're not doing anything , your body still is, and that takes energy. Actually, since you rest for about a third of the day, you spend more energy on resting than anything else.

Physical activity

Obviously you spend energy whenever you move. From your bed to the shower in the morning, from home to work or school, and any other activity. Even when you're sitting or standing, your muscles expend energy so you can keep yourself up. The amount of energy you spend that way in a day will depend on what you do: some people don't need to do much physical activity like the office worker who

travels by car and some do a lot more physically demanding labor i.e. a manual worker, or someone

who walks or bikes a lot.

Sport and physical exercise also increase the

amount of energy spent. For example, a 121 pound

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 (no activity) and 50 %

(lots of activity) of your daily caloric expense. The bottom line is: the more physically active you are, the more energy you're going to have to use to do those activities.

Interestingly, exercise affects your OUT in two ways: first, it raises your daily expenditure the days you train. 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 standpoint, than a pound of fat.

Muscle contracts when you move, is put under stress when you train and constantly rebuilds itself to sustain its daily effort. As we have seen, energy expenditure 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 physical activity in that same day.