Chris van Tulleken, a London-based infectious diseases physician and BBC broadcaster, makes a forceful case that 'ultra-processed food'—a category defined by Brazilian nutrition researchers and now codified in the NOVA classification system—is a distinct public health threat from merely 'processed' food and has reshaped global eating in ways doctors are only beginning to understand. The book combines van Tulleken's own one-month, eighty-percent-UPF diet, conducted under the supervision of colleagues at University College London, with reviews of the epidemiological and mechanistic evidence linking UPFs to obesity, metabolic disease, cardiovascular disease, depression, and early mortality. He argues that UPFs are best understood not as food but as industrial products engineered—through textures, flavor combinations, and price points—to override the body's satiety signals and to be eaten in greater volume than whole foods. Drawing on conversations with formulators, food industry insiders, and addiction researchers, van Tulleken describes how a small number of transnational corporations now structure what most people in rich and middle-income countries eat. The book is also a personal reckoning with his own appetites and with his twin brother Xand's experience of obesity. It has been credited with shifting public conversation about food in the UK and is now driving similar debates in the US.