Obesity and breast cancer are two very frequent pathologies in the world today, which have a strong impact on society. Various research studies have tried linking the two. For this purpose, data was collected from the medical histories of 524 women who had been diagnosed and treated for breast cancer from January 2009 to September 2010. The objectives of the study were to find and verify a possible association between the nutritional state of these women and their age when they were diagnosed with the tumour (p < 0.0001) as well as a statistically significant association (p < 0.0001) between the age of the first menstruation and the nutritional state of the patients. The results obtained showed that obesity was closely related to breast cancer.