Science in sport advanced isolate 1kgsis advanced isolate is the latest addition to the sis protein range offering a high quality whey protein isolate shake to support the growth and maintenance of lean muscle mass the product contains 100 pure whey protein isolate with added leucine this low carbohydrate and low fat protein shake contains 5g of leucine and 9g of branched chain amino acids bcaas to stimulate and support the growth of lean muscle mass to maximise training gains each serving