What kind of exercise you do, the key is to lose more weight, which depends on the calories you consume when you exercise. However, a coach once told me that when it is cold, people tend to store fat. When you swim, your body is stimulated by cold, which may consume less fat than when you run (not calories, of course, swimming has many benefits. I have been working out for about 8 years, and I have never seen anyone swim to lose weight successfully. On the contrary, I have seen many successful running to lose weight. If your knees are bad and you feel uncomfortable running, you can swim more. If you run, you will get used to jogging from the beginning of walking slowly. Although they are all exercises, I think running is the main thing and swimming is the auxiliary thing.