The aim of this study is to investigate how excess weight can influence cancer risk and the possible mechanisms involved. For this purpose, a bibliographic review was made of the studies published between 2000 and 2024 that analyze this relationship, as well as specific types of cancer associated with obesity. A significant association was found between overweight/obesity and increased cancer risk. Some specific cancers such as esophageal, stomach, colorectal, liver, and endometrial cancers, among others, are particularly sensitive to this relationship. Therefore, excess weight is confirmed as an important risk factor for the development of cancer. Maintaining a healthy weight and following healthy lifestyle recommendations are essential to prevent cancer and improve survival in cancer patients.