First of all, we are talking about reducing body fat, not just weight. Walking fast consumes a lot of calories, but this heat does not come from the decomposition of fat, but from the decomposition of glycogen in the body. Fat will not decompose until glycogen is consumed. Fat decomposition is very troublesome, and you need to exercise until your heart rate reaches 60%-70% of your maximum heart rate (a simple algorithm for maximum heart rate: 220- age). This requires more vigorous exercise to achieve. It usually takes at least 30 minutes to run at a constant speed. The amount of brisk walking can't reach this level at all, so it's not a question of how many pounds you can lose in a month, but you can't lose fat at all. What's more, if you do it three times, aerobic exercise is best done once. Because continuous exercise can increase your heart rate and eventually reduce fat. Do it three times. Every time the heart rate increases, stop exercising and never reach the fat-reducing heart rate. Therefore, it is better to walk for 45 minutes three times than to run for 45 minutes.