> Ah ok, well, obesity incidence is probably almost entirely explained by the amount of sugar and fats in modern diets.

The obesity epidemic started rapidly around 1980, but it's unlikely diet changed for the worse since then.

Also, it happened to lab animals and pets as well.

https://royalsocietypublishing.org/doi/abs/10.1098/rspb.2010...

Also, it appears to be correlated with low altitudes and interventions that cause you to move to higher altitudes cause weight loss.

https://journals.plos.org/plosone/article?id=10.1371/journal...

> Purely anecdotally, my step-dad always thought he was intolerant to gluten because of his reactions to British bread, but when he spent a lot of time in France and tried bread there, he was fine.

The American equivalent of this (people who go to Europe and think the bread is healthier because it's easy to digest) is because we fortify wheat and the extra nutrients esp. iron cause stomach discomfort.