Quark is a product that falls in a gray area and can be tricky to define nutritionally. It can occasionally be used as a 4-oz. protein serving for women and a 6-oz. serving for men. It can also be used as a 2-oz. fat serving if it is the full-fat version. You may also check the nutritional information of a product that you commonly use as a protein and as a fat, and then compare the Quark product to it and use accordingly.