Here's a cool graphic for seeing how glucose metabolism declines in an addicted brain...and how it slowly recovers with abstinence. This example involves cocaine use. No one yet knows what the same sequence would look like in porn users, but judging from what guys on the forum experience as they recover, it's likely there would be some of the same changes involved.
Pull the slider across the bar to watch the action. I saw no enticing ads on this page.