Brain Energy

Hello Coaches!
I have a question about our brain capacity. I think that Brooke has said that our brain has a certain amount of energy it can expend in a day so we should use it wisely. So I just really want to know how sugar, flour, tv, and other types of buffering can take up most of its energy and how much. Even decisions of deciding what to eat or where to go for dinner takes up energy. I find this all so fascinating honestly and just want to know more. I also noticed with myself that I really do my best thinking in the morning and early afternoon. I was working on getting my blog up and running and then creating my first post before noon. I got it all done and then went to work and did my first client’s hair from noon to 2pm and then I was done. I did not even want to finish my day. Is it possible to use up my energy for the day? Just wondering. Thanks in advance for the insight!