Ultra-processed foods and human health: the main thesis and the evidence.

This first paper in a three-part Lancet Series combines narrative and systematic reviews with original analyses and meta-analyses to assess three hypotheses concerning a dietary pattern based on ultra-processed foods. The first hypothesis-that this pattern is globally displacing long-established diets centred on whole foods and their culinary preparation as dishes and meals-is supported by decades of national food intake and purchase surveys, and recent global sales data. The second-that this pattern results in deterioration of diet quality, especially in relation to chronic disease prevention-is confirmed by national food intake surveys, large cohorts, and interventional studies showing gross nutrient imbalances; overeating driven by high energy density, hyper-palatability, soft texture, and disrupted food matrices; reduced intake of health-protective phytochemicals; and increased intake of toxic compounds, endocrine disruptors, and potentially harmful classes and mixtures of food additives. The third and final hypothesis-that this pattern increases the risk of multiple diet-related chronic diseases through various mechanisms-is substantiated by more than 100 prospective studies, meta-analyses, randomised controlled trials, and mechanistic studies, covering adverse outcomes across nearly all organ systems. The totality of the evidence supports the thesis that displacement of long-established dietary patterns by ultra-processed foods is a key driver of the escalating global burden of multiple diet-related chronic diseases. Two companion papers in this Series specify policy actions and wider public health strategies to promote, protect, and support diets based on fresh and minimally processed foods and prevent their displacement by ultra-processed foods.