The government is supplying the obese with a slimming drug Wegovy. But the ancient world was dominated by the emaciated, and the fat were extremely thin on the ground. They were therefore the subject of considerable interest.

A degree of corpulence was the sign of a rich, healthy and prosperous man. But obesity turned one into a figure of fun or ignominy: it demonstrated an inability to control one’s appetite for luxuries. The 8th Ptolemy of Egypt was so fat that it was impossible to put one’s arms around his stomach. His son was equally fat and incapable of walking without leaning on people, though loved dancing at drinking parties. Dionysius, the ‘gentle, reasonable’ tyrant of Heraclea, was so fat that he choked when he fell into a deep sleep. Long, thin needles stuck into his sides and belly woke him up. He conducted business sitting in a box from which only his head extruded.

The vast politician Python used his bulk to good effect. When the people of Byzantium were quarrelling with each other, he tried to unite them by saying: ‘Look how fat I am. But my wife is even fatter! When we are getting along, any little couch has room enough; but when we are fighting, the whole house isn’t big enough!’

Doctors saw it as unhealthy to eat more than the body could bear without exercising it off. They observed that retired athletes very often ran to fat in that way (the humourist Lucian claimed the athlete Damasias was too fat to be allowed into Charon’s boat to cross the river Styx). Spartans took a stern government line on weight: every ten days their soldiers were checked, naked, for excessive thinness or corpulence. The Roman doctor Celsus advised losing weight through late nights, worry and brutal exercise, while the thin should put on weight through rest, constipation and big meals.

In the light of their views about obesity, the ancients would have found the modern world baffling. For it is the poor who seem to be fat, not the rich. How on earth did the poor do it? What were the rich doing with their money?