Cog, it is not just that excess sugar it poison, it is also the fuel cancer needs to grow on.
Good for you that you took the time to learn this and took control of your own heath. I have never done the full blown keto or IF stuff, but I avoid excess carbs in general.
Yeah, fats are mixed. But some look to be really clear, trans-fats are crap. OTOH, I would take most natural fats over sucrose any day.
Alas GBM and other brain tumors are not effected much by avoiding sugar/carbs as the body has a highly regulated system to maintain a constant glucose level within the brian.