You should burn 500 calories using the training session. Along with the 750 to 1000calories that are reduced by the diet, you lose healthy calorie amount on a daily basis.
Do cardio as it burns the most of the calories. Increase the difficulty and duration of the training gradually otherwise you are at risk of injury. Walk thirty to 45 minutes, three times a week and after couple of weeks, increase the frequency and duration. After few months you can try fitness workout, bide riding or swimming.
When finished with the fitness training, continue with interval training. This training has alternating sessions of training that is intensive and short periods of rest. It gives amazing results. Warm up and run 2 minutes or walk twenty to thirty minutes of hard work out.