It's worth making sure you don't go too low on carbs, the Newcastle diet is a calorie controlled diet, not carb counting.
Remember you need glucose as energy for your brain.
Estimates can be up to 120g a day.
It's ok to have a ketogenic diet, and feed the brain that way, but if you aren't eating enough carbs, and then not enough fats, you'll be living off body fat, then converting that into ketones. You still need glucose though, your body will convert amino acids from your bodies protein, unless you make sure you are eating protein.
This is getting more complicated, uses more energy, and is starting to become different to the original Newcastle diet. I'm not saying worse, or better, just be aware you are changing it, and you are really starting to push your body into true starvation mode.
About 25% of the energy for your brain should be/needs to be glucose, it's worth making sure you keep at least that in your diet, and 30g is about 120 calories out of your day, even if you do go ketogenic. Otherwise it's the full 120g.