An individual’s daily protein requirements vary based on lifestyle, lean body mass, and personal goals. The commonality is with the protein intake of the general population is it is usually too low. Protein is important for tissue repair, maintenance/growth of lean mass, many metabolic functions, and as something very important for our purposes, healthy metabolic rate. When dealing with performance nutrition or any type of plan to optimize body composition, protein is the base of the meal plan. Protein is metabolically expensive which means it requires more energy to be digested and absorbed than the other macronutrients. At the same time it is not an efficient source of energy. This means higher protein intake serves to enhance or maintain healthy metabolic rate, especially when running at a caloric deficit.
Example: I had a 210lb athlete come to me already on a structured meal plan. His daily intake was 300g carbohydrates, 80g fat, and 200g protein. By changing nothing besides adding 150g protein (+600 calories from protein) there was a 4.5lb weight loss in 7 days as the body adjusted to the change.