Not eating one type of food doesn't translate to cutting overall calories. Besides, fat can help you feel full after eating, which may curb your desire for seconds or dessert. Your body needs some dietary fat to function.
Less than 10% of your calories should come from saturated fats, say government dietary guidelines. Replace butter and processed foods with more healthy polyunsaturated and monounsaturated fats, like olive oil, cold water fish, tofu, avocado, and small amounts of nuts.