The Keto diet is the best diet for maintaining muscle mass. Other low cal diets--especially ones that encourage equal protein/carb--will allow muscle loss. Take a good look at Weight Watchers/Jenny Craig "success stories." Their BF% have decreased, but they have lost a ton of muscle--they are jsut smaller, fat people. A ketogenic diet, through biochemical processes, permit better muscle retention. The use of AAS will always maximize retention during a ketogenic diet.
I have talked about using rHGH along with a ketogenic (low carb) diet for fat loss and "cutting." The advantage is that there is no effect on the HPTA--where using AAS, you will need to do recovery. Of course, the major disadvantage is cost. Both rHGH and AAS will act to preserve muscle mass, albeit with different biochemcial pathways.
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