i would ask your doctor for a deffinate answer, but tbh i wouldnt think it would lead to any more weight loss, i was on Xenical and my diet in general was healthy and low fat, i just struggled with snacking etc, so i didnt see a major diference with regards to the tablets because as you take them with every meal and my meals werent high in fat it didnt really need to do much, so if you took one with SF, which doesnt have anywhere near 15g of fat in, it wouldnt really do that much, and remember your body needs some fats!!
x