> People’s diets were “worse” in the past — full of lard and bread — because diet doesn’t cause obesity. The ~1% of people who were obese in the past were people with one of the various medical conditions known to cause obesity, such as Prader-Willi Syndrome, hypothyroidism, or hypothalamic lesions.

This is a very strong claim that is lacking a source. There are entire groups of people in history that were documented to be obese, especially in religion or sports.