this does not have to be an ‘either – or’.
Let me start off by saying that the majority of his weight loss success will come from caloric reduction. For somebody to ‘burn off’ fat through exercise alone requires an awful lot of exercise.
A balance of cardiovascular and strength training will be the best exercise approach. Mind you, for cardio to be in support of weight loss, it should be at least 150 minutes a week and ideally more. Whether or not your client is well enough conditioned to do this is up to your judgment. A strength routine, maybe two times a week and designed to have a cardiovascular component, should condition the client to be able to improve the intensity of cardiovascular exercises. At the same time, it will prevent the client from actually losing muscle mass. When a person loses weight, it is not only fat but also some muscle, and that’s what you are trying to prevent.
Hope this helps.