Obesity and metabolic disease in migrants: a role for the gut microbiome?

Migration, while often motivated by safety, education, or economic opportunity, often heightens the risk of obesity and metabolic syndrome. Resettlement in industrialized nations is associated with sedentary lifestyles, irregular sleep schedules, and Westernized dietary patterns rich in ultra-processed, high-fat, and high-sugar foods. These changes disrupt metabolic homeostasis through endocrine and circadian dysregulation, promoting insulin resistance, visceral adiposity, and systemic inflammation. Migration alters the composition and diversity of the gut microbiome, suggesting that the characteristics of the microbiome could be important in linking migration to changes in health outcomes after resettlement. However, the precise mechanisms underlying these microbiome-mediated effects remain poorly understood. We propose that a dynamic metabolic interface is reshaped via a rapid "microbiome acculturation", which is a process by which the gut microbiome rapidly adapts to a new cultural and environmental milieu, such as caused by migration, shifting from traditional, fiber-rich microbial profiles to Westernized, Bacteroides-dominant communities associated with metabolic dysfunction. This is characterized by the depletion of fiber-fermenting Prevotella and enrichment of Bacteroides species, leading to reduced short-chain fatty acid production, impaired gut barrier function, and increased endotoxemia. Dietary transitions, chronic psychosocial stress, circadian disruption to night-shift work, and reduced physical activity experienced by immigrants reshapes gut microbial composition and function to a pro-inflammatory milieu and enhancing insulin resistance. Thus, gut dysbiosis serves as both a biomarker and mechanistic driver of post-migration metabolic deterioration, integrating dietary, behavioral, and environmental stressors into a unified pathogenic pathway. Effective prevention should target the gut-brain-metabolic axis using multidimensional strategies: restoring microbial diversity using high-fiber, prebiotic, and probiotic nutrition; promoting physical activity and circadian alignment; and addressing social determinants of health such as work patterns, food access, and acculturation stress.