Answer:
Long answer
Proteins are the building blocks of the body, each and every organ muscle and skin and cells are made of proteins. They can also be used for providing energy to the body in a state where other energy sources aren't available.
Fats are stored energy blocks which can be used by the body at its own convenience whenever there is a deficit of energy in the body. They can also be directly burnt to give energy in cases where energy needs of the body are not met by dietary intake
Carbohydrates are the most convenient and preferable source of energy in the body and are easily converted to give out immidiate energy to the body, excess carbohydrates can be converted into fats and stored for later usage as and when required by the body.
Proteins, fats and carbohydrates have many secondary functions and roles in the human body. If you are keen to know anything more specific feel free to ask.
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Short answer :</h3>
Fats are used for energy after they are broken into fatty acids. Protein can also be used for energy, but the first job is to help with making hormones, muscle, and other proteins.
