Well Walking is awesome jogging is even better if you have great knee's. It’s a great way to build stamina, but what i want to point out here is just walking alone isn't going to help. The best way would be to do train with weight and do the cardio natural way.
If may suggest, I suggest this book in case of you are a beginner or an intermediate. there are several fitness books but most of them are not what the public needs and, they can’t train the way a bodybuilding, weightlifting trains.
Here is a book where i have outlined specifically what workouts for beginners or intermediates. whether you want to build muscle or lose fat, fitness industry is full of myths and it’s important to see and understand what works for us and what doesn't.
Now coming to the question and looking at it in detail, weight loss and fat loss are two different things and its often misunderstood. If you just want to be fit and healthy then skipping along with jogging three a week is more than enough. It will help you not only in feeling better but also will help you be slim and fit. Progressively you can build on running more often and covering more distance and then try to beat your PR’S. but a word of caution if you run on a regularly make sure you rest well and monitor your knees for wear and tear. Good diet and well rested body is vital to recover.