If you're a beginner, start by walking 3 days per week for at least 15-20 minutes. Gradually increase the frequency and duration of your walks until you are walking 30-60 minutes per day, most days of the week.t a weight loss rate of ½ -1 pound per week, it will likely take you at least 20 weeks to lose 20 pounds. Losing weight at this pace is safe and will help you keep the weight off long term.