I've read his book Brain Energy, and I think that he has some good ideas. But I am skeptical that mitochondria and energy metabolism will tie everything in mental health together any better than a neurotransmitter approach has. I wrote about this a year ago : https://medium.com/invisible-illness/is-ketosis-the-key-to-mental-health-dd32d5643df7

In some ways it could be just a manifestation of broken brains all tend to have some commonalities to how they fall apart, as I wrote about here: https://medium.com/wise-well/one-grand-factor-aims-to-explain-all-mental-health-conditions-8d549d87445c

At a practical level, keto diets may be worth trying, but if they don't work for a given individual they shouldn't be blaming themselves for not trying harder or enough. In my response to my YouTube video on the same topic, I did receive comments from a few people who felt that they suffered either ongoing or permanent physical and mental damage from trying keto diets. These bad reactions appear to be rather infrequent.