The main order of business is to lower cortisol, a secondary one is to re-establish adrenergic receptor sensitivity.
Look at things that can raise cortisol during a workout:
- How hard you are pushing each set
- Psychological stress (being intimidated or psyched up by a weight/exercise)
- Neurological stress (complex workout, new exercises, circuits, alternating movements, etc.)
- Training fasted
So right off the bat if you have a cortisol problem you should bring these down. And YES it means essentially training in a suboptimal way. But right now your goal is to fix you. If you can MAINTAIN muscle while doing that, it’s a huge bonus. Don’t try to make gains until you feel better. What you will need to do to stimulate gains will make your problem worse.
This means a low volume of work per session (5-6 sets per muscle and no more than 12 per workout), low effort… leave 2-3 reps in the tank on every rep. Only use exercises you are very comfortable with and don’t train fasted.
Of course, lowering your life stress will be the most important factor.
You can also use some supplements to help out. Glycine post-workout (3-5g) and in the evening will help decrease cortisol and adrenaline.
Magnesium at 500mg (ideally magnesium taurate) at the same times to dislocate the adrenaline from the adrenergic receptors to help resensitize those receptors.
Rhodiola when waking up to balance dopamine, adrenaline and serotonine.
As for nutrition, it’s not time to try to lose the fat. A caloric deficit, especially with low carbs, will increase cortisol levels even more (one of the main functions of cortisol is mobilizing stored energy and elevating blood sugar levels when they are too low).
Honestly, until you are fixed, forget about improving your physique. It sucks to hear but you need to get back to health and a lower stress situation before being able to push hard again.