Packaged food optimization as an industrial, scientific process only really became a thing after WWII. Before that the effects were insignificant at the population level.
I'd argue that it's a few thousand years old. Humans didn't evolve to live on grains, but for the last few thousand years we've gotten the bulk of our calories from rice & wheat flour.
The other reply is correct in that I was speaking to a broader concept than just historically recent industrialization, but yes, that certainly accelerated things too.
Thousands of years may refer to domestication of e.g. corn.