Day 3 of IF so far. Its so very close to what I was already doing when trying to lose fat. I am at about a thousand calorie deficit mostly from cardio and by the time its time to eat am hungry enough to eat my running shoes. I imagine with less of a deficit it will be a bit easier.
I have to admit though, I am not sure I would want to do this while trying to gain maximal lean mass. I think it would just feel wrong to be unfed for such long periods of time. Right or wrong, I always took the feeling of being good and sore as an indication that I should be eating to give my body the nutrition it requires to rebuild and grow.
You can grow easily on IF when going for mass. Feeling like you need food 24/7 to grow is purely psychological.
As a matter of fact, the insulin release and anabolic response you get breaking fast is nothing that can be duplicated with a traditional diet. Anything lost by not being fed a few hours, is more than made up as soon as you start eating again.
Of course you have to hit your desired macros, as is with any diet