I've read a number of things as well as watched a number of videos. The following I think is a good summary of some of the things that I mentioned:
Particularly, starting at 5:45 in the video, gets into the metabolism aspect.
With regard to carbs and workouts, a number of sources say that carbs aren't necessary to fuel a workout. Certainly people who follow a Ketogenic nutrition plan and stay in Ketosis don't have carbs as an energy source. The idea with Ketosis is that your body will produce Ketone bodies as fat gets metabolized that are then used as an energy source. Also, note that the big thing with Ketosis is that it's common to see people consume too much protein, and their macro ratios aren't right to produce Ketosis, and therefore protein will end up as glucose via the gluconeogenesis process.
For me, I'm not doing a full Ketogenic plan, but again, just pushing my carbs to post workout. The idea being that keeping the insulin low by not eating carbs or excessive protein keeps one in fat burning mode, and then post workout, spiking the insulin (not excessively so) by eating some fruit (bananas are good for this) and then getting more protein in.
That stuff comes from the Carb-Backloading Protocol. CBL incorporates Ketogenic aspects coupled with Intermittent Fasting. That's essentially what I'm doing. I consider the IF part the most important for the results I've gotten, but honestly I think nutritional timing may play more of an important role than I realize. I'm not sure.
Personally, I've worked out fasted, and have also done 5 mile runs fasted. Running I actually find that I have consistently better runs while fasted (even if I have been fasted for 16+ hours). With workouts, I don't know if I notice a quality change while fasted or not fasted. I've had stellar workouts fasted, but it does take some getting used to.
Having said that, most of my workouts are not fasted, but are also not carb-fueled. My first meal of the day consists of eggs and sauteed greens and slivered almonds (in olive oil). This is usually around noon. Calorically, this meal isn't that high, even though it's higher in fat. My big meal of the day is definitely my post workout meal.
I workout around 2 or 3 pm usually, then come home and eat carbs and protein. With the carbs, in the CBL protocol, the carbs are supposed to be simple carbs, not complex carbs, so as to get an insulin response quickly, and also so that the carbs are processed quickly, and therefore insulin levels return to a lower state earlier in the evening, allowing the fasting/fat burning process to pick up again.
On non workout days, I tend to eat less, and sometimes do only a single meal for the day.
At minimum, I think IF helps people zero in on the right amount of food to consume. Again, we're all different, so the proper amount of food for me is different for you. But again, I think IF is a good way to figure out that right amount, and get one off of the regular food intake train that we're taught we need to be on. And of course, some people do need to eat that often.
So, ultimately, I'd say check out the video, and also read some stuff on Carb Backloading.
There's a youtube channel, called Kinobody - run by Greg O'Gallager. He does IF, and has a couple videos on his channel showing what he eats for the day. He's been doing IF for over 6 years. And while he's genetically gifted, he also works out hard. He's got a strong personality, which I like, but some people might be put off by him. For what it's worth.
Hope this helps
EDIT:
I wanted to add - ease into the IF thing. I started out by just pushing my first meal until 10am. If I got hungry, I drank (decaf) coffee, with a little bit of milk. Some people say don't even have milk, to not consume anything that will result in an insulin response, but I've found personally that a tiny bit of milk doesn't break my fast - and I can feel when I'm fasting. After a week, I pushed to 11am. Another week, pushed til noon.
I've been doing IF for a good 9 months now, and I am completely used to it. I don't get hungry in the morning any more, even when I can feel that I'm in the fasted state. And, hunger if/when it comes (sometimes at night) does NOT produce low blood sugar effects for me. It all feels very natural and good to me. Again, I think of the low blood sugar effect that we get between meals almost as a withdrawal symptom to the eating habits most of us know, because the insulin levels stay at a certain average level, and we've become accustomed to that.
Also, if you're working out in the morning, CBL and IF is still feasible. It just means that the eating window should be adjusted to suit your needs.
And finally, both Terry Crews and Hugh Jackman do IF (HJ uses IF when getting ready for movies). I don't know if that holds any weight (no pun intended), but it's interesting none-the-less.