This is easily demonstrated by logic and a few facts without actually cutting into somebody's brain. The brain runs 30% more efficiently when it runs on ketones. In other words, it does 30% more work for the same fuel, or it does the same work for 30% less fuel. Consequently, eating a ketogenic diet would allow the brain to grow 30% bigger. In fact, it would probably allow the entire body, except fat tissue, to grow significantly bigger. Because if the brain runs 30% more efficiently, the entire body would also run 30% more efficiently.

Remember the Zucker rats Taubes talked about? Their fat tissue remained intact while their lean tissue was shrunk to compensate. Or rather, whatever caused their fat tissue to grow and stay big also caused their lean tissue to shrink and stay small. In this case it was a genetic mutation but isn't it reasonable to assume that this genetic mutation acted exactly on the same mechanisms that dietary carbohydrate act on to achieve basically the same goal?