Can you elaborate on this? I only personally know one person who works at Google, and haven't heard about this decline.
A personal observation regarding eating not tasty food:
I served in the Israeli army, eating 3 meals a day on base. The food was perfectly edible... But that's the best I can say about it. People noticeably ate less - eating exactly until they weren't hungry and nothing more than that, and many lost a few kilos.
While ever larger obviously can't work in the theoretical sense, I think the original post still stands for why the ideal population is larger than it is now. For the past 150 years, the prices of resources have been falling, and their availability rising. When this trend stops - there'll definitely be an argument for halting growth. But as things stand now, it seems clear that we're still below capacity.