Hi. Look, there are no hard , fast, rules here, but for fat loss, the optimal approach with weights would be to stil stay somewhat moderately heavy, but keep rest periods short. Sets, well, that really depends. For instance, I would suggest circuits for fat loss, first, strength, second. Say you pick out a full body circuit consisting of 8 exercises. You go from one to the other prety quickly. One circuit might be enought, but two would expand the work time. Now, lets say you pick three movements only, say one for lower body (squat or deadlift), dip (upper body push), and chin (upper body pull), then to maximize working time , calories burned, metabolic rate, then maybe do them in a circuit about 5 times. On the other time, if not worried about fat loss, but going for strength and size, the same circuit, with lots of weight piled on, may be fine for one to two working sets after a lighter warmup or two, with lots of rest taken in between exercises and sets. It all dependes on what your end goals are, and there are no hard fat rules, just general guidelines.