The article kind of misses the forest for the trees: just as today, diet was associated with various conflicting theories and advice - some reasonable, some pure fabrication. In absence of much hard evidence food becomes a playing field for "systems" that assign values to foodstuffs. Also, obviously, sugar played a different role in societies in which the calorie requirements of physical labour were a much bigger challenge than obesity.

Also: "beans, which were thought to cause flatulence"? I'm pretty sure that bit is factual.