Obesity is a major risk factor for cancer, contributing to approximately 20% of all cancer cases. The risk is influenced by factors such as diet, weight changes, body fat distribution, and physical activity. Obesity is strongly associated with cancers of the endometrium, esophageal adenocarcinoma, colorectal, postmenopausal breast, prostate, and kidney, while less common cancers include leukemia, non-Hodgkin's lymphoma, multiple myeloma, malignant melanoma, and thyroid cancer. The mechanisms linking obesity to cancer involve insulin, insulin-like growth factor-I, sex hormones, and adipokines. These include chronic inflammation, oxidative stress, crosstalk between tumor cells and adipocytes, obesity-induced hypoxia, shared genetic susceptibility, and immune dysfunction. Obesity increases cancer risk through various biological pathways, including hyperinsulinemia, insulin resistance, IGFs, sex hormones, and adipokine production. Lifestyle factors such as a hypercaloric diet, sedentary behavior, and low physical activity also contribute to cancer risk. Obesity-induced hypoxia and oxidative stress further increase cancer risk. Genetic susceptibility and endocrine disruptors also play a role. Obesity is linked to reduced immune function, particularly in natural killer cells. Surgical interventions such as bariatric surgery have shown a reduction in cancer incidence in obese patients. While the exact mechanisms are not fully understood, obesity significantly increases cancer risk, and weight management may reduce this risk. The review highlights the importance of understanding these mechanisms to develop effective prevention and treatment strategies.Obesity is a major risk factor for cancer, contributing to approximately 20% of all cancer cases. The risk is influenced by factors such as diet, weight changes, body fat distribution, and physical activity. Obesity is strongly associated with cancers of the endometrium, esophageal adenocarcinoma, colorectal, postmenopausal breast, prostate, and kidney, while less common cancers include leukemia, non-Hodgkin's lymphoma, multiple myeloma, malignant melanoma, and thyroid cancer. The mechanisms linking obesity to cancer involve insulin, insulin-like growth factor-I, sex hormones, and adipokines. These include chronic inflammation, oxidative stress, crosstalk between tumor cells and adipocytes, obesity-induced hypoxia, shared genetic susceptibility, and immune dysfunction. Obesity increases cancer risk through various biological pathways, including hyperinsulinemia, insulin resistance, IGFs, sex hormones, and adipokine production. Lifestyle factors such as a hypercaloric diet, sedentary behavior, and low physical activity also contribute to cancer risk. Obesity-induced hypoxia and oxidative stress further increase cancer risk. Genetic susceptibility and endocrine disruptors also play a role. Obesity is linked to reduced immune function, particularly in natural killer cells. Surgical interventions such as bariatric surgery have shown a reduction in cancer incidence in obese patients. While the exact mechanisms are not fully understood, obesity significantly increases cancer risk, and weight management may reduce this risk. The review highlights the importance of understanding these mechanisms to develop effective prevention and treatment strategies.