Actually, the ketogenic diet is usually recommended for those who struggle to metabolize glucose. Limiting other sources of calories causing the liver to release ketones puts the body into a famine mode. This is not healthy for most. If the brain is trying to get energy from glucose but the supply is limited, problems could arise. The ketone system is designed to provide energy to the brain and nerves to keep them alive as a last ditch effort to stay alive during fasting or famine.

Your brain needs meat protein for the amino acids it contains. The natural fats in meat and dairy are good for the brain. Coconut oil is a good natural fat along with olive oil. Most plant based fats pale in comparison.

Whole grain carbs are good, too. High density sugars should be limited. Small amounts of high density sugar are OK, especially if they are combined with other foods that slow the absorption. A teaspoon of sugar is only 18 calories. A small piece of chocolate (Hersey's individually wrapped) is only 80 calories. They should not be a problem in moderation. The dopamine response of that pleasant taste is good for the brain. I usually have such a piece of chocolate in the evening.

PCS is tough enough without the frustration of not enjoying the occasional taste pleasure.

If you like popcorn, coconut oil is great for popping corn. Then, a light spray of olive oil and a light sprinkling of salt is a healthy and tasty snack. Much better than microwave popcorn. If you need instructions, just ask. I've been popping popcorn in a pan on the stove since the 60's.