In terms of the overall health and function of the human body, protein is essential for building and repairing things. Your organs, muscles, skin, hair, nails, bones and certain hormones are all made up of some amount of protein. It’s an absolute requirement for sustaining life and proper function.
When dietary protein is in short supply, the body tends to take protein from skeletal muscles to preserve more important tissues and body functions. As a result, lack of protein leads to muscle wasting over time. Amino acids (found in protein) consumed in excess of the amounts needed for the synthesis of nitrogenous tissue constituents are not stored but are degraded; the nitrogen is excreted as urea, and the keto acids left after removal of the amino groups are either utilized directly as sources of energy or are converted to carbohydrate or fat.
Protein will help you lose fat, build muscle, and generally get your body to look and perform the way you want it to look and perform.
Your goal is to get your body to burn nothing but fat and leave all of your pretty muscle alone. Eating a sufficient amount of protein on a daily basis is the key dietary factor in getting your body to preserve your muscle and burn fat instead. In addition to preserving muscle, building muscle has two dietary requirements, a calorie surplus and eating a sufficient amount of protein on a daily basis. Protein is the “building block” of muscle. Without enough of it, your body just cannot (and will not) build muscle.
Another major role protein plays in losing fat revolves around its thermogenic properties. Protein is the macronutrient with the largest thermic effect. Therefore, eating more protein on a daily basis will actually lead to more calories naturally being burned by your body.