Where does your body get the energy it uses for work?

Answer 1

The short answer is the food you eat. However, that's a little too bland. The foods we consume contain lipids (fats and oils), proteins (amino acids), carbohydrates (sugars and starches), and other chemical compounds that keep energy stored in their chemical bonds (alcohols, nucleic acids, etc.). When you eat, your body digests the foods and extracts the compounds through the intestines. The circulatory system picks up the nutrients and circulates them through your body to your cells. To some degree, all cells store some energy. In the case of neurons, little energy is stored, whereas adipose (fat) tissue stores a great deal of lipids. During physical activity, the cells consume available stores of energetic compounds (carbohydrates, proteins, and lipids) in order to keep working. After prolonged activity, the stored energy is depleted and the cells begin to take up carbohydrates from the blood. Once these supplies are depleted, the body goes through a complex process of converting stored energy from fat into usable energy. As a result, it usually takes a great deal of exercise to "burn off" fat.

Answer 2

Most of the fuel you use during exercise doesn't come from the food you've recently eaten! It actually comes from the carbohydrates (called "glycogen") and fat that's stored in your muscles, liver, and fat cells. That's enough to fuel 1-2 hours of very intense exercise or 3-4 hours of moderate intensity exercise.

Answer 3

From the food you eat.

The digestive system provides carbohydrates and protein to the body's cells, and stores fat as well, and the cells can use cellular respiration to extract energy from the chemical bonds of the food.

Answer 4

from the food you ate