no, you're both oversimplifying. the brain needs some glucose to sustain itself, a little bit, according to present day research. yes, it can principally functi

no, you're both oversimplifying. the brain needs some glucose to sustain itself, a little bit, according to present day research. yes, it can principally function on ketones but not /exclusively/. it is not controversial that the brain can survive long periods of time on principally ketones, but what has not yet been proven (for obvious ethical reasons) is whether or not the brain can sustain itself with absolutely no glucose whatsoever. again, the ratios are key. i'm not contesting that ketones can be used as the principal fuel source, just that "the important thing is ATP" because the brain needs some glucose. https://www.ncbi.nlm.nih.gov/books/NBK28048/ https://www.ncbi.nlm.nih.gov/books/NBK28048/