Foods that are rich in proteins are called high-protein foods. A high-protein diet is often recommended for bodybuilders and athletes to help build muscles and lose fat. A balanced diet incorporates good amount of protein that helps to build muscles a reason protein is called the building block of the body. However, it is advisable to consume protein in moderation as too much of it can harm the internal organs, especially kidneys. The best sources of protein are dairy products, eggs, fish and meat.