I'm doing my drive-by points on IF...as many were already covered:
- IF is just a tool and not a diet, make it work to your lifestyle ...and it doesn't need to be everyday
- Make sure you are getting in enough protein everyday
- Many do IF on non-workout days and eat bigger meals of mostly protein (and less calories than workout days)
- You will of course need to gauge performance and body composition and whether you need to adjust IF days, calorie intake, etc.
- You can take weekends off too and just eat more flexible
- You can also do Warrior diet style on workout days and eat light all day and a bigger meal at night
As for fasted workouts and cortisol, try the brand "Chained Out" BCAAs pre and during the day...as it is supposed to have a cortisol blocking agent (of course I can't verify this...but talking to someone who works for them and knows his sh*t, people are seeing results using it...and doing no other changes to their diet/workouts).
On a side note...unless you are a bodybuilder, I think many worry too much about cortisol...as it is a natural process and has a half life of like 2 hours (unless you are one stressed out person). Much like autophagy, where you recycle proteins (especially damaged ones) is a factor in longevity/health. There are also theories of protein pulsing and how the body can upregulate protein synthesis when needed to over 24 hours if you have the protein to use. So in a sense....making sure you get enough protein in every day is still your top priority. Then dump some BCAAs in a big water jug and carry it around all day to sip on it. Adjust all other macronutrients/calories around it to meet you performance/body comp goals. It's really not all that hard, just need to keep it simple and know when things need to be changed up.