I know it's mentioned in the article for long term but for the first couple weeks was there any difference in brain functioning? I'm not talking about anything severe, but if you have a job where you are using a lot of brain power, I'd imagine very low carb diet seems to be a little counter-intuitive. Like the article said the brain gets energy from ketones but is it the same amount/enough energy as regular carbs? Do you feel slightly slower, possibly more tired when performing longer challenging tasks? I've dieted very strictly before with a lack of carbs but also a huge deficit of calories and couldn't think nearly as quick. I agree lack of calories was the primary reason for this but it also seems very low carbs could contribute to constraining optimal brain output.