Evolutionary mismatch between stomach capacity and modern diets: Implications for obesity and metabolic disease.

Human gastrointestinal anatomy evolved under conditions of food scarcity, low-caloric-density diets, and high physical activity. In this context, a relatively gastric-accommodation stomach capacity conferred a survival advantage by allowing consumption of large volumes of fibrous, low-energy foods, buffering seasonal shortages, and maximizing intake during rare periods of abundance. Modern food environments, characterized by constant access to energy-dense foods and sedentary lifestyles, have reversed these selective pressures, creating an evolutionary mismatch between ancestral digestive physiology and contemporary diets. This narrative review explores how a digestive architecture shaped by scarcity may become maladaptive in modern high-calorie conditions and examines stomach capacity as an under-recognized contributor to obesity and metabolic disease. Evidence was synthesized from evolutionary biology, anthropology, gastroenterology, and metabolic medicine using literature identified in PubMed, Scopus, and Web of Science (1990-2024). Evolutionary and anthropological evidence suggests that increased gastric volume was advantageous in both pre-agrarian and agrarian societies. In contrast, in modern environments this trait may promote excessive energy intake, delayed satiety, and metabolic dysfunction, particularly in the presence of ultra-processed foods. Clinical observations from bariatric surgery support this framework, as surgical reduction of gastric volume induces rapid metabolic improvements, often preceding significant weight loss. Gastric accommodation capacity, once adaptive, may now contribute to metabolic disease in obesogenic environments, reframing obesity as a predictable consequence of evolutionary mismatch.