Overweight people now outnumber the hungry across the world. Hurrah! Famine, one of the gravest threats to human life throughout history, one of the four horsemen of the apocalypse, is on the wane! Imagine the celebrations if we heard that tranquil boredom was outdoing war, or vigorous immune systems were outdoing pestilence.

But why I’m the only one breaking out the paper hats and balloons? The International Association of Agricultural Economists, which has revealed that one billion of the world’s six-and-a-half-billion population are too heavy and 800 million are malnourished. “Obesity and excess weight,” says Professor Benjamin Senauer, “bring with them significant risks of chronic disease and premature death.” But not as significant, I would guess, as starvation.

People talk a lot these days about the “obesity epidemic”, as though you could catch obesity by sitting too close to a fat person. Perhaps that’s why there’s always an empty seat next to me on the subway. And while I would be the first to support better public transport and designing cities to make walking easier, I’m afraid that these measures are not going to make fat people thin.

Absolutely everyone knows how to lose excess weight. Eat less, exercise more. The physics of it is simple. The question, then, is: if it’s so simple, why is anyone overweight? Some people are overweight because they like it. Some people believe that they are in charge of their own bodies, are allowed to be the weight that pleases them, and find a larger body pleasing. Some people are overweight because they simply lost track of their eating habits for a while. With time, they will adjust their lives to suit them better.

Finally, many people are overweight as a reaction to emotional problems. This is an answer you may not like if you believe that all emotional problems can be dealt with by drinking a nice cup of tea and listening to the shipping forecast. I believe it is this group that is growing. People are getting fatter because food is now readily available; it’s easy to eat emotionally because food is everywhere. And if governments really want to sort this out, they would be better off investing its money in extra therapy.