its like adding something brilliant to something that is already awesome, resulting in amazingnessss.
why would a yogi want to be in ketosis? well, i have a billion reasons for you, but i'll cut it down to a few.
ketosis is known to enhance mental clarity, and that's putting it lighting. Basically people, who i can't find the reference to right now, say that depending on what kind of fuel you are giving your brain, it will cause areas to work differently. (i know your brain will always use some glucose but like some ketones get in there and see what happens. the brain will run on 70% ketones after 4 days of no sugars.)
when a person is in ketogenesis the detailed part of your mind (who needs math anyways) is reduced allowing for the part that regesters patterns, big pictures, to function better. It also enhances your perepherial vision and ability to take in many stimulus at once without being way overwhelmed.
first and foremost, eliminating the insulin spikes makes you much more stable, mentally and emotionally. I've even noticed my physical balance has imrpoved in the last 6 months. I no longer dance in Natarajasana.
It provides super mental clarity and better focus, making dharana (training the mind to focus) a simple task. All those annoying thoughts that pop up and start chattering about your roommates bird shitting everywhere tend to vanish. This makes dhyana, or meditation, not just easier for your sitting practice, but to carry throughout the day. I've noticed how quickly i can fall into a meditative state now, and how i pick up on my emotions before they pick up on me.
with this kind of clarity, it is much easier to listen to your emotions, and control your outward senses while also being more aware of them (uhhumm speaking of prathayara here.)
also, there are no scientific studies, but from personal and read experiences people tend to need less sleep on a ketogenic diet. I sleep 6-7 hours and wake up to a dance party with my cats, only to end the day at 11 with another dance party and tea. here is an article: http://www.sleepwarrior.com/use-ketosis-to-train-your-brain-to-sleep-less
so you can see, a ketogenic diet totally backs the yogic lifestyle from a meditation stand point. This provides insight as to why yogis may have fasted so frequently, especially before retreats. Also seems to be evidence for how yogis could have meditated for days with little sleep. Even Native Americans were known to fast before hunt outings. In order to track an animal a person needs to be stable for long periods of time, aware of their surroundings, able to pick on on the surroundings and the pattern of the animal and focused!
it is also well known to help with eliplepsy, preventing the icky seizures.