To burn fat, you must do low intensity exercise. It takes about 15 minutes to start burning fat. After that point, you want to keep exercising for at least 45 minutes to one hour, or even longer if possible. High intensity exercise burns your carbohydrate stores in your muscles and liver, which leads to craving carbs afterward. That means NO RUNNING and NO AEROBICS!! Pick something that you enjoy, walking, biking, swimming, or a sport. Walking is a wonderful exercise, enjoyable, prevents osteoporosis, low intensity so it burns fat, and also if done outdoors is very refreshing, getting some sun on your skin (without getting burned) gives you Vitamin D and Calcium. You should be able to hold a conversation while you exercise. Start with 5 or 10 minutes per day if needed, and work yourself up to one hour or more. Do it at least 5 days per week.
To build muscle, weight training (resistance training) is best. (Do not attempt weight training on your own without the guidance of a personal trainer or your docotr.) By increasing your muscle mass, you increase your metabolism. This means that you are always burning more calories, so it is easier to lose weight and easier to maintain your weight. It also prevents osteoporosis. Building muscle tones your body and makes you lose INCHES. You may not lose WEIGHT as fast, but you lose FAT and INCHES faster. That’s because muscle is much heavier than fat. Overall, in losing weight, weight lifting is the best exercise possible.
Remember that it takes 15 minutes to start burning fat. Make each session last at least 45 minutes, ideally an hour or more. If you are dividing your workout, you may try 15 to 30 minutes of weights and then walk for as long as possible.