Some new ones discovered today:

Central Heating. Central heating means your body needs to expend less energy to heat itself, reducing calories out, and therefore you get fat. (Corollary: Air Conditioning should make us skinny. Also, Grok must have been a really good calorie counter in order not to starve to death in the winter. Or maybe he had a mirror that he checked himself out in every week so that he could know to eat more a bit more at each meal if he got too skinny because of the cold.)

Quitting Smoking. People gain weight when they quit smoking. Lots of people have been quitting smoking, therefore the obesity epidemic.

Both theories from here:

https://health.spectator.co.uk/geor...er-explanation/