For more than 30 years, participants regularly responded to dietary questionnaires,
Food frequency questionnaires, so epidemiology only. I do wonder why the correlation exists if we can control every other variable, if frying them would be result in a higher correlation with T2D? Does the type of potato matter? But of course such experiments can't be done.
I have not forgotten and do have an enameled cast iron bathtub. It is fantastic.