It is advised to brush your teeth at least twice a day, but when? Just before bed is a gimme because you're about to lie mostly still for 6+ hours. Best to not leave food particles to fester.
What's the best time for an earlier brushing? After breakfast? After lunch? After work/school?
Plus, what's up with TV and movies having breakfast scenes where they get up and head right out the door? Did they already brush and now they're going to leave food to fester all day? Eww.
But then you walk around with breakfast breath all day?
After breakfast and/if going out and then before bed.
Is breakfast breath worse than lunch breath or dinner breath?
I don't know. But it seems very wasteful to brush teeth and then eat because then you have a lot of food particles and bacteria still.
Better to eat breakfast and then brush because then you have a fresh breath and no unnecessary gunk and bacteria in your mouth the whole day.
As someone else said: food softens the enamel and makes your teeth more vulnerable so brushing right after breakfast may cause way more damage. I always brush my teeth before breakfast and almost never have any problems with my teeth. I know that my friends who frequently need treatment for their teeth brush them after breakfast.
But that's of course anecdotal evidence that doesn't say much, and I'm no dentist, so I may be wrong.