Obesity and type 2 diabetes have a constantly increasing prevalence in industrialized countries, and both are associated with an increased risk of developing certain cancers. The mechanisms that contribute to this association are probably multiple and are based mainly on hormonal and inflammatory changes. In view of this unequivocal relationship, it is necessary to act upstream by optimizing diabetes prevention and cancer screening measures in at-risk populations. This article reviews the epidemiological data, the physiopathological link between these entities and the concrete measures to be applied in clinical practice.