Your body performs better when your body temperature is slightly higher. A warm-up, especially in the early morning, helps raise your body temperature so you experience a slight improvement in performance. The American Council on Exercise also notes that you may experience greater efficiency in calorie burning when your core body temperature is higher.
Your body gives up on exercise when too much lactic acid builds up in the blood. Without a warm-up, lactic acid can build up quickly, making a workout seem nearly impossible in the first few minutes. If you warm up, however, your energy systems adjust to the increased demands, and lactic acid builds up less quickly and suddenly. As a result, you can work out longer and harder.
Walking can help you lose some extra pounds faster. You should walk fast enough that you are in the moderate-intensity exercise zone at 60 to 70 percent of your maximum heart rate. You should be breathing harder than usual and can speak in full sentences, but you couldn't sing. You can use your heart rate and exercise zone reading from a fitness band, app, or heart rate monitor to ensure you are exercising at moderate intensity.
Always warm up for five minutes at an easy pace no matter what duration you will be walking. At a brisk walking pace, you would burn 100 to 300 calories in 30 minutes (depending on your weight) or 200 to 600 calories in an hour. By walking for 30 minutes or more at a time, some of those calories will be from stored fat. During the first 30 minutes of exercise, your body is burning sugars stored as fuel. These are used up after about 30 minutes.