Calories can be used to measure any kind
of energy, but people most often associate
the term with nutrition. One calorie is the
amount of energy required to raise the
temperature of 1 gram of water by 1
degree Celsius (1.8 F).
Because that’s such a small unit of
measure, food energy is measured in
kilocalories (1,000 calories). The numbers
you see on nutrition labels are still marked
as calories, because in nutrition, calorie
and kilocalorie have become synonymous.
Where the calories come from
Carbohydrates, fats and proteins are the
types of nutrients that contain calories,
and that means they’re the main energy
sources for your body. The amount of
energy each nutrient provides varies.
-Carbohydrates are the food
nutrients that your body uses first.
During digestion, they’re released
into your bloodstream and
converted into glucose, or blood
sugar. When there’s a demand, the
glucose is absorbed immediately
into your body’s cells to provide
energy.
If there’s no immediate demand,
glucose can be stored in your liver
and muscles. When these storage
sites become full, excess glucose is
converted into fatty acids and
stored in fat tissue for later use.
-Fats are an extremely concentrated
form of energy and pack the most
calories. When digested, they’re
broken down into fatty acids, which
are also used for energy or for
other body processes.
If there’s an excess of fatty acids, a
small quantity can be stored in your
muscles, but most of them are
stored in fat tissue. There’s
virtually no limit to how much fat
your body can store.
-Proteins have many responsibilities
but can also supply energy for
physical activity. This can happen
if you consume too few calories,
eat excess protein, or if you’re
involved in prolonged physical
activity. Any excess calories from
protein are converted into fat and
stored.
Vitamins, minerals, water and fiber
don’t contain calories. However, they’re
still vital to your health and well-being.
When they’re lacking from your diet, you
increase your risk of serious illness.
Other substances in food, such as
cholesterol, don’t provide calories
either.
