Illustration by Nicola Jennings

When I saw the photograph I could scarcely believe it was the same country. A picture of Brighton beach in 1976, featured in the Guardian a few weeks ago, appeared to show an alien race. Almost everyone was slim. I mentioned it on social media, then went on holiday. When I returned, I found that people were still debating it. The heated discussion prompted me to read more. How have we grown so far, so fast? To my astonishment, almost every explanation proposed in the thread turned out to be untrue.

Unfortunately, there is no consistent obesity data in the United Kingdom before 1988, at which point the incidence was already rising sharply. But in the United States, the figures go back further. They show that, by chance, the inflection point was more or less 1976. Suddenly, at around the time that the photograph was taken, people started becoming fatter – […]