If an athlete says to me that a thing he does to his body work 95% of the time, I would consider to try it, and already did, some things against over-the-counter conventional medicine like this no-carb diet.
Note that this doesn't effect my opinion of fat as a great energy source. I personaly eat a relatively low carb (not keto), high-ish fat, high-ish protein, moderate carb diet. I'm also very active and this seems to work for me so far.
I think people need to let go of the idea that ketosis is some sort of "special" state. It's just a metabolic state that's been suppressed by modern eating habits. Three meals a day and snacking is a cultural invention; not a biological necessity.
A lot of athletes prefer to exercise in a ketogenic state. I know personally I'm able to run farther if I've spent the day fasting than if I had a big meal at lunch. (I don't have the same initial burst, but I don't hit a wall either) (Not to mention that digestion is a very expensive process)
I think what's more unnatural is that modern eating habits are designed around blocking any sort of ketogenic state, which is where the easiest weight loss comes from. (Also, I need to lookup a reference for this, but I think I remember reading that fat burns a bit "cleaner" than sugars. Less free radicals I think? Something like that)
[For people unclear what I'm talking about with ketosis: basically, your body burns glucose first for energy. Then when there isn't sufficient glucose, it starts burning fat. The burning of fat for energy is what's known as ketosis. (I know I'm probably vastly oversimplifying). The thing about fat burning is it only kicks in at a significant level when glucose is depleted though. So if you're exercising while eating a chocolate bar and drinking a gatorade... well the exercise is good! But you won't lose weight)
That may have been a bit of a fad though. The single most important rule that I know of is to never mix an animal protein meal and sugar, because that creates triglycerides which harden your blood vessels. This single rule is why fast food is so bad. Cheeseburgers are fine, but add fries and a pop and you just blew it.
As I've gotten older, I've noticed that my need for carbs has diminished greatly. As a teenager, I frequently ate a bag of gummy worms and a 2 liter bottle of pop on weekends. That changed to a case of beer in college. Either of those sound untenable today though.
The single easiest bit of advice I could give someone to lose fat is to stop eating all white fluffies and all sugar. So eat peas, salads etc with each meal instead of corn/bread/potatoes. Then pump iron at least 3 times a week so your body is in a constant rebuilding mode.
You don't really need to watch your fat intake like they recommended 20 years ago either. Always opt for natural fats like avocado, peanut or almond butter and regular butter because you need those to rebuild your connective tissue.
The big secret that nobody ever tells young people is that bodybuilding is all about eating/exercising in ways that elevate your hormones, then strengthening your connective tissue. If you do those things, then muscle and endurance come automatically. If you don't do them, you'll always be emaciated and will eventually get injured.
Of course, Keto is a thing, but I haven't heard many stories of bodybuilders that actually target the keto-state. It's about getting the right amount of carbohydrates (hint: not as much as most people eat).
Unless they're prepping for a contest, which is not what they spend the majority of their time doing.
Bodybuilders typically consume about ~30% protein. Where did you get the idea that it is mostly protein? Not to say that there aren't outliers obviously.
Just about every bodybuilder slams carbs, all day long.
While true, I would't say that everything bodybuilders are doing is worth following. Many pros do things that are extremely unhealthy. It isn't just the abuse of anabolics, but also insulin - which is relevant to what we're discussing here. There are bodybuilders with type 2 diabetes due to their unhealthy habits while trying to get bigger.
At least in modern societies. Of course the Inuit and other far-north peoples have known forever that one can live healthily off essentially nothing but meat.
Note than balance does not mean soda is the bulk of your calories (that should be a straw man, but I see many people who drink that much soda).