Need to no please important?

im 15 and weigh about 13 stone and height 6 3 and big build but i need to tone up and lose some weight for rugby as just been scoted for leeds and need to no is it dangerous to take this http://www.argos.co.uk/static/Product/partNumber/9000991/c_1/1%7Ccategory_root%7CSports+and+leisure%7C12108128/c_2/2%7Ccat_12108128%7CNutrition%7C12108371.htm