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Exercise vigorously. Include regular aerobic activity. Include weight training. Plan one to two rest days.
The best way to lose weight quickly is a calorie controlled diet and exercise.  You will need to participate in a fairly intense exercise regimen to burn a significant amount of calories to help you lose 20 pounds quickly.  Vigorous exercise is any activity that significantly raises your heart rate and breathing pace.  You shouldn't be able to say more than one or two words at a time without taking a breath.  On the perceived exertion scale you should be around a seven or eight out of ten.  Level one is sitting and ten is the most intense exercise you could perform. Set aside about an hour every day.  Plan to be active for an hour most days, even if some activities are less strenuous than others. Moderate intensity activity will also burn calories and support weight loss.  However, vigorous intensity activity burns more calories and may help you reach your weight loss goal quicker. Prior to starting any exercise routine, it's important to meet with your doctor to make sure exercise is safe and appropriate for you. You should aim for a minimum of 150 minutes of cardio weekly.  However, it's recommended to get up to 300 minutes or five hours weekly for increased weight loss. Common cardiovascular exercises include running or jogging, swimming laps, dancing, cycling, and certain martial arts. These activities burn differing numbers of calories per hour, but all of them are effective. Strength training is a healthy and highly effective type of exercise for weight loss.  It will help increase lean muscle mass, which over time, can increase your body's natural ability to burn calories.  Weight training is invaluable for any weight loss program, because stronger muscles require more energy to operate, which means that they burn more calories.  Include about two days of strength training for at least 20 minutes a session.  Exercises include:  weight lifting, weight lifting classes, body weight exercises and pilates. Taking a break from exercising is a crucial part of a workout schedule.  Continually working out, especially at vigorous intensities, is a lot of work and stress on your joints, muscles and body.  Rest days help your body recover and can help prevent injury. Stick to rest days just as religiously as you stick to your workouts. Rest days should still be active.  That means staying off the couch and participating in light, low-impact, low-intensity activities.  These can include:  restorative yoga, light walking, or a leisurely bike ride.