The author Johann Hari believes the new generation of weight-loss drugs, which includes Ozempic, Wegovy and Mounjaro, will prove as era-defining as Prozac or the contraceptive pill. He’s probably right, and yet it takes a certain boldness to write a book assessing their impact now, while the drugs are still so new. Ozempic, a brand name of the medication semaglutide, was first approved as a diabetes treatment in 2017 and hit Hollywood as the ultimate diet drug around five years later. Wegovy – semaglutide at a slightly different dosage, prescribed specifically for weight loss – has been available on the NHS since…