Abstract

The global coexistence of obesity and type 2 diabetes mellitus (T2DM), frequently termed “diabesity,” represents 
one of the most pressing metabolic challenges of the 21st century. This narrative review synthesizes 
epidemiological, mechanistic, clinical, and public health evidence to elucidate the bidirectional and multifactorial 
relationship between obesity and T2DM. Obesity significantly increases the risk of T2DM through interconnected 
pathways involving insulin resistance, β-cell dysfunction, adipose-tissue endocrine dysregulation, chronic low
grade inflammation, and lipotoxicity driven by ectopic fat deposition. Additional mechanisms include alterations in 
gut microbiota composition, genetic and epigenetic variations, and life-course exposures beginning in early 
childhood. The review highlights distinct obesity phenotypes, particularly metabolically unhealthy obesity, 
visceral adiposity, and ectopic fat patterns, as more strongly predictive of diabetes than BMI alone. Conversely, 
metabolically healthy obesity appears to confer comparatively lower but still elevated risk. Clinically, intentional 
and sustained weight loss improves glycaemic outcomes and can induce diabetes remission, while pharmacologic 
and surgical interventions further support metabolic recovery. Public health evidence underscores the need for 
multisectoral strategies targeting food environments, early-life nutrition, and community-level lifestyle 
interventions. Despite extensive research, critical gaps persist regarding causality, genetic interactions, 
longitudinal trajectories, and the mechanistic contributions of microbiota and environmental exposures. 
Advancing precision-based prevention and treatment approaches requires integrated, multi-omics, and life-course 
studies to deepen understanding of the obesity, T2DM nexus and inform more effective interventions.