I remember a letter sent to the Financial Times some time last year from a farmer who claimed it wasn't surprising that obesity rates have increased because nowadays, with the ubiquity of central heating, we expend less energy simply on keeping warm, but we haven't reduced our calorie intake to compensate.
The Letter (from march 2018) claims:
Your statement that “the rise in total energy intake through diet is the main cause of rising obesity levels” cannot be true because in the UK calorie intake has trended down both recently and indeed for over a 100 years. ... The scientific reality is that, being mammals and warm-blooded, nature intends that some 70 per cent of our calorie intake should be used to generate heat ... The reality — as every farmer knows — is that weight gain increases in warm accommodation. In short, modern obesity derives from the introduction of universal central heating, heated cars, and heated workplaces.
But I've been wondering about this letter for a while. Is there any evidence to support the hypothesis?