It is true that brains can use ketones for energy and concentration instead of sugar? This video (and my roomate) claim they can. I thought brains only operate on glucose and the liver is required to turn fat into sugar?

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My limited understanding is that fat does not get converted to glucose only to ketones. Protein can be converted into glucose (sugar) by gluconeogenesis.

Ketones are used by the brain, though apparently only for 70ish percent of energy use.

It should be noted that the amount of carbohydrate needed by the brain is not actually that high. Lyle Macdonald sets the amount of carbohydrate a day needed to prevent ketosis at around 100g (~ 400 kcal) from a literature review.

  • That's not entirely correct. The glycerol backbone of fats is converted to glucose though gluconeogenesis. The fatty acids attached to that backbone get converted to ketones, and the neurons are able to use ketones.
    – stix
    Aug 22, 2022 at 17:37

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