Cancer is one of the leading causes of death in the world.Accumulating evidence indicates that obesity is strongly associated with the development of cancer.This review aims to understand the underpinning mechanism of how obesity contributes to the development of cancer.As obesity is an exaggeration of normal adiposity associated with extreme chronicity and co-existing conditions,true causality and underlying mechanisms are difficult to evaluate.Moreover,the exact causal relationship is yet to be established.Therefore,it will be unlikely to outline a"one system fits all"mechanism for this obesity-cancer axis;however,the biological processes linking obesity and cancer need to be better understood.In this review,we tried to portray the postulated mechanisms considering common pathophysiology associated with obesity,leading to cancer progression.Obesity-mediated insulin metabolism,sustained low-grade inflammatory signaling,elevated estrogen metabolism,and abnormal microbiome diversity and dysbiosis are among those mechanisms that can lead to tumor and cancer progression.