As a recently qualified fitness instructor I would recommend as already suggested that you follow a varied exercise programme.As well as aerobic exercises[walking,jogging cycling,aerobics classes]I would recommend that you also follow a light weights programme to improve local muscular endurance which will tone your muscles and increase muscle mass which will in turn help with weight reduction.Flexibility exercises are equally important in that they help to reduce the risk of injury which will enable you to continue exercising.Abdominal curls or sit ups will work your upper abdominal muscles.