Medicine can treat obesity, but can’t agree on what obesity is

IN THE SPACE of less than a decade, medicine acquired a means of doing what millennia of diets and exhortation could not. A new class of drugs, GLP-1 receptor agonists, can strip a fifth or more from a patient’s body weight. This week Britain became the second large market, after America, to make one such treatment, Novo Nordisk’s Wegovy, available in tablet form as an alternative to injecting it.