It's quite amazing. I can eat and eat and eat, and not feel sated. Rest of the month, I have good cues to stop eating and easily recognise when I've had enough.
Scanning google seems to say we do need a few extra calories before/ during but like not two pints of ice cream and lots of toast 
I did find a thing that says new research does actually show our brain needs more glucose, but don't have the energy to hunt through the 'research' to see if it's shonky science?
But I feel like the change in hormones does something to leptin and gherkin?