A person's ability to add muscle while not gaining fat, or while actually losing fat, is highly individual. For instance someone who is out-of-shape, can easily put on muscle while losing fat, through starting a simple basic exercise program. Too bad for most of us it does not stay that easy. As we all know, it becomes more difficult as you get in better shape to achieve the same rate of re-partitioning. But how quickly this occurs and to what degree will vary from person to person, is dependant on a wide variety of factors, and the solutions will vary with the individual as well, and may well include hormonal supplements. I just think such broad statements as "it is not possible to gain muscle while not gaining fat" distract from the basic principles of proper training and nutrition and favor the mindset that roids or other cheat methods are the only way to achieve the desired result. This weak mindset is unfortunate and precludes many from accumulating the sweat equity that will make them less reliant on the roid cycles to maintain that well-earned foundation. As far as cycles go, most people tend to eat more to get the maximum benefit and roids can also have varying direct effect on the appetite. So as far as gaining muscle vs. fat goes, it will vary with the state of training of the individual and their diet. If the individual was very highly stagnated in their training and the muscles really primed, the addition of the hormone could partition the right nutrients very efficiently to muscularity. While for the less advanced athlete, the higher caloric intake could be partitioned less efficiently with more fat accumulation. Regarding 1-AD specifically, somebody else could better speak as to how it would stack up in comparison to other pro-hormones or roids regarding nutrient partitioning. In general though I think real world results can be highly individual based on the variety of factors and influences I have touched upon.