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What are Calories?
In order to understand the logic behind low calorie diets of any kind, one
must first understand what exactly calories are. A common misconception is that
calories somehow measure the amount of food you take in. A calorie is actually
a unit of energy.
Specifically, a calorie is the amount of energy, or heat, required to raise
the temperature of 1 gram of water to 1 degree Celsius (1.8 degrees Fahrenheit).
Though we often associate calories with food, calories can be applied to anything
that contains energy.
To further confuse things, when labels say that a food contains a certain amount
of calories, they actually mean kilocalories. (1 kilocalorie equals 1,000 calories.)
Food calories are always given in kilocalories to make it easier for people
to calculate the number of calories they require in a day.
Over the years, people have abbreviated kilocalories to calories when discussing
food. Note, however, that a food calorie is actually equal to a kilocalorie,
not a calorie. (This is why some food labels measure calories in Kcal.) For
example, a chocolate bar that contains 277 calories according to its label actually
contains 277, 000 calories (in the energy sense) and 277 kilocalories. Confused?
Think of it this way: kilocalories and food calories are used interchangeably.
However, an actual calorie is a much, much smaller unit that measures
energy. (Thus, for the remainder of this article when we talk about calories,
we’ll actually mean food calories, or kilocalories.)
The number of calories in a food is a measure of how much potential energy
that food contains. When we eat, our bodies "burn" the calories in the food
through metabolic processes. During these processes, enzymes—proteins that carry
out chemical reactions in cells—break down the ingested foods into forms usable
by the body.
Enzymes break the carbohydrates down into glucose and other sugars, the fats
into glycerol and fatty acids and the proteins into amino acids. These different
forms then flow through the bloodstream to the cells. The cells take what they
need immediately for energy, and store the rest.
Even if the food calorie content isn’t listed on the label, or if you’re eating
products without product labels (like fresh fruits and vegetables, for example),
you can still determine the calorie content yourself provided you know the carbohydrate,
protein and fat content. Just remember these three figures:
- 1 g Carbohydrates= 4 calories
- 1 g Protein= 4 calories
- 1 g Fat= 9 calories
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