We will look at what happens when you train fasted and from there we can look at whether it is a good option or not.
The first thing we need to consider is that fasted training will lead to higher levels of cortisol and adrenaline.
First cortisol because when you are fasted it is higher anyway. The main function of cortisol is to mobilize stored energy and, along with glucagon, increase blood glucose level when it’s too low.
If you are fasted (especially if you are physically active) blood sugar drops down so you will need to release more cortisol to keep it at normal levels.
When you train this will be magnified because of the higher energy expenditure, even more so with MMA which tend to rely heavily on glucose for fuel.
Cortisol also leads to an increase in adrenaline. Specifically, cortisol increases the conversion of noradrenaline into adrenaline. By leading to a higher baseline cortisol level, fasting also gives you a higher adrenaline level. That’s why a lot of people report having more energy when fasting.
Now, the higher adrenaline will allow you to train hard. It can increase strength, power and speed. It also has a positive impact on reflexes and speed of thought. If it is not excessively high. If it becomes too high then it can lead to issues by increasing muscle tone so much that it reduces muscle extensibility (makes you tight) and makes you overthink and overreact.
But that is rarely an issue in training, it would be more of a problem when competing.
The main issue with fasted training then becomes an excessively high cortisol production, which, if it stays elevated, could slow down recovery (diminishing glycogen replenishment, reducing protein synthesis, increasing protein degradation). And as for the higher adrenaline level, this could lead to beta-adrenergic downregulation, the most common cause of what we call “overtraining”.
Now, if you have your meal right after, a lot of these problems can be mitigated, at least the adrenaline one. But cortisol might still remain an issue.
EAA would not help in that they will not prevent the release of cortisol and the increase in adrenaline. You need to consume carbs and elevate blood sugar for that.
I will obviously preach for my own parish and recommend PLAZMA. But objectively it would still be the best choice as the carb in plazma will not cause a reactive hypoglycemic response like you would get from other carbs. And the electrolytes will also greatly help you because another big issue with fasted training is that you might be dehydrated or have low electrolyte levels going into the workout (even if you drink throughout the day, if you don’t also take in electrolytes, it can actually make things worse).