The title is terrible, it should read ketosis/ketones may prevent, reverse age-related effects within the brain.
"Low carb" as the title currently reads does not necessarily result in ketosis and your body/brain running on ketones, which appears to be the scope of this study. There is more to dietary ketosis than low carb, just as an example carnivore or paleo diets are low carb, but those will generally not result in ketosis, in protein rich diets your body will convert the protein to glucose which will continue to be the primary fuel for the cells in the brain/body.
If you have never entered ketosis and experienced your brain running on ketones, I would suggest you experiment for yourself. I would say a minimum 2-3 months which should be enough time for your microbiome to change and your body/brain to adapt primarily running on ketones.
"Low carb" as the title currently reads does not necessarily result in ketosis and your body/brain running on ketones, which appears to be the scope of this study. There is more to dietary ketosis than low carb, just as an example carnivore or paleo diets are low carb, but those will generally not result in ketosis, in protein rich diets your body will convert the protein to glucose which will continue to be the primary fuel for the cells in the brain/body.
If you have never entered ketosis and experienced your brain running on ketones, I would suggest you experiment for yourself. I would say a minimum 2-3 months which should be enough time for your microbiome to change and your body/brain to adapt primarily running on ketones.