The safest rate for weight loss is no more than two pounds per week. In the first week of a healthier lifestyle, you can lose a bit more with extra fluid loss, but maintaining a steady pace of one to two pounds per week is the most successful long-term method of weight loss. To determine how long it will take, divide the number of pounds you hope to lose by 1.5 or 2. This will give you an estimate of how long it will take to reach that point.