The down low is that, for various reasons, a ketogenic diet (very low carb and high fat, or moderately low carb and high medium chain triglyceride, such as coconut oil), seems to allow our mitochondria (the cells' energy factories) to make energy more efficiently.  This ability is less important in our muscles (unless you are an elite athlete), but in our brain, which uses a ton of energy and relies on energy-expensive ion gradients to function properly, efficiency is paramount.

Meaning their brains are struggling with the metabolism of glucose and are running on anaerobic pathways instead.