In January 2023, Johann Hari started to inject himself once a week with Ozempic, one of the new drugs that produces significant weight loss. He wasn't alone - some predictions suggest that in a few years, one in four of the British population will be taking these drugs. While around 80 per cent of diets fail, someone taking one of the new drugs is likely to lose up to a quarter of their body weight in six months. To the drugs' defenders, this is a moment of liberation from a condition that massively increases your chances of diabetes, cancer and an early death. Still, Hari was wildly conflicted. Can these drugs really be as good as they sound? Are they a magic solution - or a magical illusion? Finding the answer to this high-stakes question led him on a journey from Iceland to Minneapolis to Tokyo, and to interview the leading experts in the world on these issues.