Protein can also manage your weight by helping to maintain lean body mass, which can increase the amount of calories that you burn in a day. Over 40% of protein in the body can be found in your skeletal muscle. Your ratio of lean muscle mass to fat mass affects the calories that are needed daily for body maintenance and weight maintenance. Compared to fat mass, lean muscle mass is more metabolically active, which means that a higher lean muscle mass can increase your energy expenditure.
Source: "The Role of Protein in Weight Loss and Maintenance." The American Journal of Clinical Nutrition. April 29, 2015.