If you ask me to describe the answer to this question in simpler words, I would rather say that our body gets energy from the food that we eat. Not just our body, but the body of each and every organism on this earth gets its need of energy from the food that it eats and even non living things such as your motorbikes and appliances get energy from the food that they eat which is in the form of fuel.
Nothing on this planet can work without taking energy in any form. Even the earth keeps on revolving around sun 365 days a year without slowing down its motion in the form of kinetic energy as it is the rule of nature that nothing works without depending on a form of energy. The way in which human body breaks down food to finally unleash energy from it can be explained as follows:-
How does the Human Body get Energy
1. We Take Food:-
The process to take energy starts with intake of food. We take food getting very much choosy. For example, if you are fat enough, you will seek for food which lacks fats. If you are prone to diabetes, you will cut off sugar from your diet. The food taken in mouth also does not reach our stomach directly, but instead it is first mixed up with saliva.
2. It Is Mixed Up With Saliva:-
There are salivary glands in our mouth which secrete saliva. When we take food in our mouth, these glands automatically start secreting saliva, which gets mixed with the food taken in the mouth. It is advised not to over-eat. This advise is given to you because of the fact that the less you eat and the more properly you chew your food, the better it gets mixed up with saliva and as saliva acts as a kind of moistening agent for food. It also helps to create food bolus and makes us get swallowed easily.
3. It Reaches the Stomach and Gets Mixed Up With HCL:-
After getting swallowed, the food ultimately reaches stomach where it gets mixed up with HCL which is also known as Hydro Chloric acid. Well, to have something acidic in your stomach may sound funny or dangerous to you, but actually the same acid helps your body to activate pepsinogen into the enzyme pepsin which then helps in the process of digestion by breaking the bonds linking amino acids.
4. The Break-Down Process Starts:-
The break-down process starts into human body during this stage where large chunks of food are broken down into smaller and smaller particles absorb-able by the body. It is also proven that the diet that you take in liquid or juice form is best absorbed by the body.
5. Our Body Gets Energy:-
Within the same process, a breakdown of nutrients like glucose, amino acids, fatty acids etc. takes place and this breakdown is what proves to fulfill energy needs of the human body. The food gets digested finally and the energy needs of human body get fulfilled. The waste product left after doing so is excreted by the body in form of stool.