One theory as to why being in a state of ketosis lowers anxiety is because the part of your brain responsible for the fear response, called the amygdala, feeds off of glucose aka sugar. Restricting sugar deprives this area of energy forcing it to power down its activity.
Most cells in the body are capable of burning fat for fuel in place of sugar, with few exceptions. If you are not consuming any sugar, the liver will metabolize some for these areas of exception. If you are not used to burning ketones for fuel, you may experience fatigue and brain fog for the first few days while your machinery adjusts to the new fuel source.
This may be partly why I’m having a strong case of writers block today so I’ll be keeping this short. It’s only day 5, I may have to pace myself!