Tbh, more data is gonna be needed. The overall body as a whole just cannot answer this question in humans conclusively.
Most of the meal frequency data and MPS is done using whey in isolation. The big limitation here is that whey digests quickly compared to mixed meals and the effects on MPS over acute periods are not equivalent.
The muscle full effect of MPS and muscle refractory effect of MPS are not fully understood nor proven. Especially with the new study in humans showing that 100 g of protein can lead to extended and sustained MPS, which suggests that distribution matters less than total intake. The 100 g serving supported MPS for greater than 12 hours post consumption: Invalid Link Removed
But this is likely going to be context dependent and dependent on what your priorities are on the whole.
If you just want some good results and adherence and enjoyment are number 1 for you, then I think we can say that variations of IF (based on the previous study I linked) are viable as long as you resistance training and get enough dietary protein alongside a reasonable net caloric intake. Will this maximize your results outright without further considerations? Maybe not.
If you planned the fasting periods of 24-36 hours at least 1-2 days post training and maybe 1 day pre next training, I think potential drawbacks are highly diminished. Remember that nutrition is permissive to growth, so after training we have higher MPS rate and the need for nutrition during the recovery/adaptation process. For trained people this can be 1-3 days depending on the study and training protocol used. Probably dont want to fast during this period overall. Probably want to make sure you have some available fuel and glycogen to perform well in the next session, glycogen takes time to build up, so eating the day before or a few meals before the next training session after an extended fasting period is likely ideal.
Acute data does suggest even mixed meals pre and post-wo with a window of 6 hours around the session may be ideal. So fasted resistance training is likely not the best option long-term.
AAS increase MPS and assimilation capacities, so again, all context specific points made above can be utilized even more alongside AAS, but you are less likely to have issues during extended fasting periods, can be a win win if timed right.
Hope I covered most of what you were asking about.
Side note, most studies using IF tend to result in weight loss bc these diets tend to result in spontaneous decreases in total caloric intakes in the participants, which means these people tend to be in deficits more then not. Some IF studies still showed increased in LBM despite this, meaning that even the unicorn, recomp, can be done with an IF options in people not on AAS. IF that does not speak to the viability of IF overall, I am not sure what does. This is the main study that comes to mind in this case: Invalid Link Removed
