The dietary fat profile that is linked to many diseases is an abundance of saturated fat and trans-fatty acids along with a relative insufficiency of monounsaturated and omega-3 fatty acids, as found in the typical American diet. Since dietary fat determines cell membrane composition, such a dietary pattern leads to reduced membrane fluidity, which in turn reduces insulin binding to receptors on cellular membranes and/or insulin action. Particularly harmful to cell membrane function are margarine, vegetable oil shortening, and other food containing trans-fatty acids and partially hydrogenated oils. These "unnatural" forms of fatty acid interfere with the body's ability to use essential fatty acids and are now linked to an increased risk of heart disease, diabetes, and cancer. Just the opposite effect is created by a diet high in monounsaturated fats and omega-3 fatty acids.