[teachingassist]

Food insecurity is an aspect of poverty and is not uncommon in the United States.

"Your eating choices" as a poor person might be to eat what and when and where you can afford to.

[username90]

Why could people manage to stay slim 20 years ago but not today? It isn't like the poor are more insecure now than back then.

[teachingassist]

The last 20 years has probably made (much) less difference than you appear to think.

From Wikipedia: "The rate of increase in the incidence of obesity began to slow in the 2000s".

But, to attempt to answer your question: e.g., the expectation that both adults in a household will work means that people/parents are more likely to be time-poor and not able to cook. Cooking skills have been lost.

[fmajid]

Eating choices are not really choices (or Hobson's choices) when you have to work multiple jobs to make ends meet and have no time left for food prep.