Ryan Quevauvilliers

How your ability to focus is dependent on your diet: Being fasted reduces parasympathetic "rest and digest" activation, keeping you alert. "Half as much caffeine will give you just as much lift as twice as much caffeine will give you on a full belly of pasta." Neurons thrive on glucose. A study published in Neuron found that "the precision with which neurons in the brain will represent things in our environment is actually much greater when there is sufficient glucose in the brain." Very low blood glucose sharpens concentration through alertness; sufficient blood glucose sharpens concentration through improved neural encoding. Overeating collapses both. Delay the first caffeine intake to 90 to 120 minutes after waking to avoid an afternoon energy crash. Do a first 90-minute focus block fasted with water, electrolytes, and caffeine. After eating, expect a dip. A second 90-minute block in the afternoon is viable if the midday meal is modest enough to avoid pushing the nervous system into parasympathetic mode. @hubermanlab