For underweight “hardgainers” or trainees looking to bulk, quality carbohydrate intake is just as important as frequent protein feedings. Weight gainer protein Bodybuilder Supplements provide a great source of complex and simple carbs, and generally digest faster then whole foods. Scientifically, protein is a series of amino acids linked together like a chain. The links that hold these amino acids together are known as peptide links. are the primary source for nitrogen in the body. Having a positive nitrogen balance is essential for proper muscle growth and repair..