I don’t know the answer but I will post what I think is most likely true for the sake of discussion.
Insulin blocks GH. This is most problematic if you go to bed with a large, slow digesting, carb containing meal in our stomach because peak natural GH release occurs in the first 2-4 hours of sleep. Also cortisol makes you insulin resistant, meaning that you will release even more insulin if you have high cortisol and food on board in the early hours of sleep, and totally block GH. IMO THIS is the basic mechanism of metabolic syndrome.
Cortisol is high (often from diet, overstress or lack of sleep)->Night time insulin is therefore high->GH is blocked->. Microtrauma/inflammation accumulates-> Cortisol is stimulated
You can plug in at any point in that cycle.
Now, as for post workout GH release, Fred Hatfield said that you should train on an empty stomach and not eat anything for an hour after training because he believed that the GH release from the workout was critical to muscular development. Keep in mind, that not only do carbs raise insulin, but so does cortisol (and non inflammatory carb can reduce cortisol release from training so it may end up reducing your night time cortisol levels to have carbs when you train even if you block post workout GH with the insulin).
Insulin has to be there to build muscle. GH is there to heal cumulative microtrauma so if GH is chronically low you will get higher cortisol, and higher insulin around the clock (basal insulin).
Most research I have read suggests that T and GH are stimulated within the first hour or less of hard training, and then done. Cortisol release increases continually the longer you train.
So I think the first points should be that if you go to sleep with high cortisol or with a lot of food on board, you are blocking the most important GH release of the day-early sleep. Second is that the hormonal effects of training are probably only going to be a NET positive if you train hard for 30-60 minutes.
If you are going to train hard for more than an hour, no brainer, you need carbs and some protein to prevent cortisol from ripping apart your muscles.
If you are going to train for 30-60 B to the W, you might benefit from periods where you train on fat/protein like eggs, meat, MCTs, coconut oil, boost your GH, and don’t eat for 1 hour after training. You won’t drive protein synthesis, but the GH and test may improve body comp and heal microtrauma. I personally don’t know what the solution is. I train for 30-60 minutes and I will go for periods where I use peri-workout carbs and protein, and periods where I go low carbs and train for GH. I would have to say that you probably can not have a workout that is both anabolic, and which stimulates significant GH at the same time.
That doesn’t mean that you should not take in carbs for short workouts, though heavy (1-3) rep sets can run virtually 100% on ATP rebuilt from beta oxidation of fatty acids.
Keep this in mind-when you are in a calorie deficit, it doesn’t matter what you eat, your total daily insulin output will be reduced, and will be fairly to very low versus your normal state. Your muscles will always have some room to put glycogen as well as fatty acids. You will be more sensitive to your own insulin. You will have less insulin blocking GH aorund the clock and at night time (basal insulin levels can plummet if you are in a calorie deficit and also if you are active) so it seems to me that when in a caloricdeficit, you will get improved GH release outside of your workout and so the peri-workout carbs will help to drive protein syntheis around the times that it will occur. In a calorie deficit, almost all protein synthesis happens in the peri-post workout window because you are not eating large enough meals the rest of the day to stimulate insulin and mTorr from the feeding effect. In other words, you have a small window of protein synthesis and a long period of low insulin but somewhat higher than normal GH levels.
When in a calorie surplus, protein synthesis is stimulated by larger feedings. Both insulin and mTorr go up after larger meals. You have general anabolism 80% of the day, and so perhaps you could train for a hormonal effect during those period where you have net positive protein synthesis around the clock, and train for anabolism (with peri-workout insulin spike) during periods where you have GH production increased during the balance of the day, and especially at night. This is kind of backwards from what our initial reasoning may be, (to train on low carbs when reducing calories and on high carbs when increasing calories) but it is what makes sense to me. Carbs peri-workout in a calorie defecit, and possibly periods of low carb training when in a calorie surplus and have increased protein synthesis outside of the training window.