I thought the brain functioned mainly on glucose. Also, what about glycogen replenishment? A 5 x 5 powerlifting program on a zero carb cutting diet seems unusual. Even DiPasquale's Anabolic Diet allows 30g of carbs/ day and a weekend carb up.
You know we're just keeping you honest DL. 
Dreamer - Don't operate any heavy machinery son. Still think you should answer my quesions in the "Yo Dreamer" thread.
Are you keeping Palmubo honest? Well he is right and true.
In regards to doing the 5 x 5 routine i didnt recomend that and i dont believe he is doing it anymore.
I have researched all diets, read the actual journals and studies, read the analysis and formulations of everyone from gurus to people who talk out their ass. I have also personally done All diets so experienced it from low cal not many meals, low cal many meals, high protein low protein, low carb, higher carb to keto.
in regards to 30 gram carb per day, he will be getting carbs indirectly from his fat sources and remaining in ketosis. Also the carbs he has stored from his cheat meal once per week and the indirect carbs will be more than enough to fuel his workouts. this pisquale fellow is very similar concept if not the same. stay in ketosis and once per week have a carb meal (this dirties the metabolism and revs it up and also gives carbs in storage for workout).
If i had my way he would train Mentzer style once per 5 days-7 days. At the most 3 times per week, whether on keto or other diet. If u know how to train u dont need more than that otherwise u are just doing low intensity shit (but that is another story and training theory debates never end so i let all do what they want).
In regards to energy levels- energy levels are more stable on keto diet ur brain loves to use ketones for fuel, also no insulin swings. also with low carbs ur brain is expecting more carbs, doesnt know if its getting them, and then eventually doesnt get them or as much as it wants...hence the feeling like shit and mood/ energy swings.
oh and the bit i forgot to mention - ketogenic burns the most fat and preserves all muscle. our aim is to burn fat. so this is the number one diet for this purpose.