Are there any good sources for a particular diet/restriction that correlates with mechanical or mental performance? Anecdotally the top performers I know generally balance meat/fruit/vegetables, eliminate sugar, and follow other common nutrition knowledge without committing to any particular diets or restrictions.
What you describe here is also set of particular diets that include many restrictions. The only difference is these restrictions are not considered extremely incompatible with the common diet.
See James Cameron's "The Game Changers":
I wish a plant-only diet was optimal across the board but so far I haven’t found the right one that is the case for me personally.
Can you please share who that was? And corroborating links?
""Speaking about his plant-based diet, the athlete said: "I'm going on and off.
"I was a complete vegan for eight years, but I would dabble into some seafood every now and then.
"Now, I dig fish.""
https://www.plantbasednews.org/culture/athlete-on-off-vegan-...
"[V]egetarianism is a commendable departure from the established barbarous habit. That we can subsist on plant food and perform our work even to advantage is not a theory, but a well-demonstrated fact. Many races living almost exclusively on vegetables are of superior physique and strength. There is no doubt that some plant food, such as oatmeal, is more economical than meat, and superior to it in regard to both mechanical and mental performance. Such food, moreover, taxes our digestive organs decidedly less, and, in making us more contented and sociable, produces an amount of good difficult to estimate. In view of these facts every effort should be made to stop the wanton and cruel slaughter of animals, which must be destructive to our morals. To free ourselves from animal instincts and appetites, which keep us down, we should begin at the very root from which we spring: we should effect a radical reform in the character of the food."