Also the per capita household expenditure on food[1] is above the average of European countries. Higher for example than in the UK or Austria, which have comparable incomes.
[1] https://www.eea.europa.eu/data-and-maps/daviz/per-capita-hou...
You don't have to go far to see the difference either: Austrians and south Germans are already much more "food-oriented" than north Germans, so this may be a regional thing rather than encompassing the whole country.
I guess you're talking about various prejudices of others. But that's a whole other topic.
I think the locals wouldn't joke about themselves that way cause to them the way they are is just "normal".
And surely you've heard Berliners say that Berlin's local food tradition is the Döner (i.e. there is no "local food")? I guarantee you no Bavarian or Austrian would say that about their own food tradition.
(And BTW I have no ill will towards Berlin or Berliners, I think it's one of the best places in the world to live in)