What is a Calorie? A calorie is a unit of energy. Technically a calorie is the amount of heat energy required to raise the temperature of 1 gram of water up 1 degree Celsius (1.8 degrees Fahrenheit).
When applied to food, we are actually talking about a kiloCalorie (1000 calories). However the word Calorie (note capitalization) is used in most literature.
The measure of Calories gives us an indication of the potential energy that food possesses. This can easily be calculated with the following formula:
- 1 gram of Protein = 4 Calories
- 1 gram of Carbohydrate = 4 Calories
- 1 gram of Fat = 9 Calories
- 1 gram of Alcohol = 7 Calories
Therefore Calories can be calculated simply by knowing the amount of these three building blocks in the food.
A politically correct pyramid with no one food group on the top or bottom. The USDA pyramid website has an unprecedented number of references to the wisdom of burning calories...
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Burning Calories
The body burns calories by a process called
metabolism. This process uses enzymes to break down the carbohydrates, fats, and proteins into materials that can be transported through the bloodstream and used by cells. Here the energy is either used immediately or stored for later. Generally the calories that are stored, are stored as fat.
Therefore if you burn more calories than you consume, you will lose weight. If you consume more calories than your body can use, you will gain weight. (Weight variance could be either muscle or fat).
How Many Calories Do We Need?
When reading food labels, the "Percentage of Daily Intake" variables are based on a calorie intake of 2000 calories per day. Obviously this is an average - everyone has different calorie averages based on their basal metabolic rate, amount of activity and exercise, genetic predisposition, and gender (among others). Men typically have higher calorie averages than women (like 2700-2800 calories per day). This is due to a higher proportion of muscle to fat.
Basal Metabolic Rate (BMR) is the amount of energy the body needs to function while at rest. This energy is used to keep the heart beating, temperature regulated, and other organs functioning. There are a number of formulas used to calculate BMR - often based around your weight. Note that the thermic effect of food also impacts on your calorie intake. This is the amount of energy your body needs to digest food.
Are All Calories The Same?
As a unit of energy, a calorie is a calorie - no matter where it comes from. BUT - in terms of nutrition, the source of the calorie is important. There is much disagreement as to the source of calories (i.e. low-carb vs low-fat).
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Metabolism
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All of the processes that occur in the body that turn the food you eat into energy your body can use. Exercise, food, and environmental temperature influence metabolism. |
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