Metabolism 101

How our bodies turn food into energy

VIV Research
September 20, 2021
Energy is taken into the body as food. We eat and drink a variety of macronutrients that include carbohydrates, fat, protein, and more.
It's digested, assimilated through the digestive tract. As the food passes through our digestive system, it's broken down, and then gets into our bodies via the wall of the intestine.
The three energy types - carbohydrates (glucose), fats (short chain fatty acids) and proteins - move into our blood. Once in the blood, it travels around the body, ready for deployment in areas where it is needed.
The brain uses 20% of the energy, directly absorbing the blood glucose. One fifth of energy goes to maintaining function in the brain. That figure remains fairly constant, without major fluctuations due to light or heavy brain activity.
The rest - around 80% - is directed by the liver to the cellular structures that need them (eg. muscle, adipose tissue, skin, digestive tract, endocrine system, respiratory system). The liver deploys most of the energy to where it's needed around the body, which varies based on time, stress, exercise and other factors.
The cellular structures "harvest" the energy using oxygen to release the energy (ATP's) - with carbon dioxide and water as by-products. The basic energy currency of our cells is ATP (adenosine triphosphate). As the cellular structures around the body take in the energy, they generate heat, and make possible muscle movement, with CO2 and H2O as byproducts of the reaction.