James Gallagher asks whether a weight-loss drug on the NHS heralds a new era in tackling obesity? He meets Jan who lost nearly 4 stone after being part of a trial taking a weekly injection of Semaglutide for 15 months alongside advice on meals and exercise. However, when people stop taking the drug the weight starts to go back on. Add to that supply shortages with heightened private demand and some doctors think the drug is as controversial as they come. James unpicks the ethical and societal dilemmas against a backdrop of half the world's population projected to be overweight or obese by 2035.

Producer: Erika Wright

Declared interests

Dr Margaret McCartney: "No conflicts to declare."

Prof Sir Stephen O’Rahilly : "in the past has been a remunerated consultant and has had research collaboration with Novo Nordisk."

Professor Naveed Sattar: "consulted for and/or received speaker honoraria from Novo Nordisk, Abbott Laboratories, Amgen, AstraZeneca, Boehringer Ingelheim, Eli Lilly, Hanmi Pharmaceuticals, Merck Sharp & Dohme, Novartis, Pfizer, and Sanofi; and grant support paid to his university from AstraZeneca, Boehringer Ingelheim, Novartis, and Roche Diagnostics. He was a co-investigator in lifestyle trials such as DiRECT and co-lead for STANDby."