Obesity contributes to approximately 20% of all cancer cases, with evidence linking it to various cancers such as colon, kidney, liver, and prostate cancer in men, and postmenopausal breast and endometrial cancer in women. Obesity increases cancer risk through multiple mechanisms, including hormonal, insulin-related, and inflammatory pathways. Weight loss, particularly in postmenopausal women, reduces breast cancer risk. Among cancer patients, obesity is associated with poorer outcomes, especially for breast cancer. Weight loss and increased physical activity are beneficial for cancer survivors, improving quality of life and reducing cancer risk. Bariatric surgery has shown significant reductions in cancer risk and mortality. However, obesity may also lead to increased toxicity from chemotherapy and radiation therapy. The use of body surface area for chemotherapy dosing may not be appropriate for obese patients, as it may result in underdosing. Obesity is associated with increased cancer risk and poorer survival outcomes, particularly for colon and prostate cancer. Weight loss and physical activity are important for cancer prevention and improving survival. The "Five A's" model (Assess, Advise, Agree, Assist, Arrange) is recommended for counseling patients on weight loss and physical activity. Obesity is a significant public health issue, and clinicians should focus on weight management to reduce cancer risk and improve outcomes. Weight loss and increased physical activity are effective strategies for cancer survivors. The role of obesity in cancer risk varies by cancer type and tumor site, with different mechanisms involved. Metformin may have protective effects against cancer in diabetic patients. Overall, obesity is a major contributor to cancer risk, and weight loss and physical activity are important for cancer prevention and survival. Clinicians should prioritize weight management and physical activity in cancer patients to improve outcomes.Obesity contributes to approximately 20% of all cancer cases, with evidence linking it to various cancers such as colon, kidney, liver, and prostate cancer in men, and postmenopausal breast and endometrial cancer in women. Obesity increases cancer risk through multiple mechanisms, including hormonal, insulin-related, and inflammatory pathways. Weight loss, particularly in postmenopausal women, reduces breast cancer risk. Among cancer patients, obesity is associated with poorer outcomes, especially for breast cancer. Weight loss and increased physical activity are beneficial for cancer survivors, improving quality of life and reducing cancer risk. Bariatric surgery has shown significant reductions in cancer risk and mortality. However, obesity may also lead to increased toxicity from chemotherapy and radiation therapy. The use of body surface area for chemotherapy dosing may not be appropriate for obese patients, as it may result in underdosing. Obesity is associated with increased cancer risk and poorer survival outcomes, particularly for colon and prostate cancer. Weight loss and physical activity are important for cancer prevention and improving survival. The "Five A's" model (Assess, Advise, Agree, Assist, Arrange) is recommended for counseling patients on weight loss and physical activity. Obesity is a significant public health issue, and clinicians should focus on weight management to reduce cancer risk and improve outcomes. Weight loss and increased physical activity are effective strategies for cancer survivors. The role of obesity in cancer risk varies by cancer type and tumor site, with different mechanisms involved. Metformin may have protective effects against cancer in diabetic patients. Overall, obesity is a major contributor to cancer risk, and weight loss and physical activity are important for cancer prevention and survival. Clinicians should prioritize weight management and physical activity in cancer patients to improve outcomes.