I spent years studying people that recovered. I learned to ask questions from anyone who got further than me. I reached out to top athletes about diet, recovery from injury and exhausted nervous systems. I've had mentors, read 100's of books, spent 5 figures on blood testing. All this served to develop my gut instinct and intuition. I combined what I learned with how i feel. Now, I can go just off feel. The truth is, we all can go off feel alone. Those of us in the chronic illness realm learned to ignore our intuition at an earl age.
Dairy seems to have a hormonal impact. It takes very little to fill up the battery. Wheat, same thing but with energy levels. It has a longer term glycogen storage effect, giving me reserves when exerting. Red meat and limited chick have the effect of replacing and restoring damage to the muscle such as tears or heavy lifting. Carbs are the main source of fuel. You can use fat as a fuel, but thats a whole other rabbit hole that isnteasily to explain.
There are lots of podcasts and youtube videos that explain this stuff now. As for game changers, you would have to pay attention to how valid arguments are structured and understand how words are used to pursuede a personal agenda. The vegan Vs Omnivore debate is all based against the standard american western processed food diet. Either one will improve health dramticly against processed food. The big thing you can do is to limit or eliminate all PUFA (poly unsaturated fatty acids) oil. This is all seed and vegetable oils (not kidding) The other thing you can do is eat high fat and low carb or high carb and low fat, but NOT both at the same time. This is all widely available if you spend time looking and googling.