When I dieted naturally I used the eca stack (I count that as natural) but I only dieted every second day. I would cut my calories and do cardio 2-3 times per day on the diet days, off days I would up them and not train at all. That way my body didn't get used to any set calorie level and it had time to recover from the damage that the heavy dieting did to it. I could generally lose 2-5lbs per weeks doing that.
Glutamine did help keep mass.