The global burden of chronic kidney disease (CKD) continues to rise, posing major public health challenges, partly driven by increasing obesity rates. Obesity has been established as an independent risk factor for renal dysfunction, with a complex pathophysiology involving renal hemodynamic changes, inflammation, lipid accumulation, and metabolic disorders. Recent research has also underscored the potential role of gastrointestinal dysbiosis and specific endothelial cell characteristics. Current evidence indicates that the impact of obesity on renal function becomes more pronounced with advancing age, partly owing to the significant structural and functional alterations in kidneys associated with aging. Furthermore, the interaction between obesity and aging exerts a synergistic effect on renal function. Sex-related differences are also observed, with males generally experiencing earlier declines in renal function, while females with obesity may face more rapid changes, although this remains a debated issue. In this review, we provide a thorough summary of what is currently known about how obesity affects renal function, focusing on age- and sex-related differences and the underlying mechanisms. Bibliometric analyses are employed to summarize and visualize the evolving trends and emerging hotspots in this field. Furthermore, we discuss methods for assessing renal function, weight management strategies, and novel treatment avenues for older individuals with obesity, offering insights for the prevention or mitigation of renal dysfunction.