Fish is a good source of protein and, unlike fatty meat products, is not high in saturated fat. The American Heart Association recommends eating fish (particularly oily fish) at least two times a week. Fish can be an excellent source of omega-3 fatty acids, essential fats that your body doesn't make but needs to function properly. A serving is 3.5 ounce cooked, or about ¾ cup of flaked fish. Oily fish like salmon, mackerel, herring, lake trout, sardines and albacore tuna are high in omega-3 fatty acids.