Obesity is a well-established risk factor for several cancers, including endometrial, breast (postmenopausal), colorectal, and hepatocellular cancers. The association is driven by various interconnected mechanisms, including chronic low-grade inflammation, hormonal imbalances (e.g., hyperestrogenism, insulin resistance, elevated IGF-1), and metabolic dysfunction. These processes create a tumor-promoting environment, facilitating carcinogenesis and disease progression. Additionally, obesity negatively impacts cancer treatment outcomes by increasing the risk of surgical complications, reducing the precision of radiotherapy, and leading to underdosing in chemotherapy. An increasing body of evidence supports the significant reduction in cancer incidence associated with bariatric surgery, particularly for endometrial, breast, colorectal, and hepatocellular cancers. While the relationship with esophageal and colorectal cancers has been previously debated, accumulating evidence now supports the beneficial impact of bariatric surgery in reducing the incidence of these cancers as well. A potential dose-response relationship between the extent of weight loss and the reduction in cancer incidence has been suggested in some studies, though further research is needed to refine this understanding. Beyond reducing cancer incidence, bariatric surgery has been shown to improve survival outcomes and lower recurrence risks in cancer survivors. These benefits underscore its potential role not only in cancer prevention but also as an adjunctive or preparatory intervention to optimize oncological treatment pathways. Despite its benefits, challenges persist, including disparities in access, variability in outcomes by cancer type, and the need for long-term data. Future research should focus on integrating bariatric and pharmacological approaches into comprehensive obesity and cancer management strategies to optimize prevention and treatment outcomes.