Years ago, I had developed tendinitis in my left ankle and had to stop doing higher intensity cardio for quite a while. I was doing a lot of step at the time. I did the recumbent bicycle for a while and then started doing Leslie workouts. I also continued with upper body weights. I gained no weight, and was able to maintain my fitness level. I was so pleased with this! I have now been doing lower impact cardio such as Leslie walks for years now and I am happier doing this type of cardio. I still do weights, Pilates, rebounding, and now Classical Stretch workouts. For me, it is a combination of diet, and consistent exercise. It does not have to be high intensity exercise to be effective. I don't think any particular type of exercise matters either. You have to do what you enjoy, and will stick with.
Sherry