If you think about the modern food environment compared to the ancient one, so let's say somebody getting something at a fair compared to the old days.

如果将现在的饮食环境,与过去的相比,例如比较在现在和过去的人们,在集市上能买到哪些东西

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

And you'll use "If I were" to talk about yourself in the present in relationship to the past.

你可以用“If I were”来比较现在的你和过去的你。

If I were 课堂 - SpeakingMax英语口语达人