To compare breast cancer metastases between obese and non-obese women and to evaluate the effect of first-line metastatic chemotherapy in each group A retrospective study was performed in an educational institute in Ireland. The study consisted of two parts: the first part was a comparative analysis of metastases development in obese (arm A) and non-obese patients (arm B). The second part was a comparison between both arms in relation to their response to first-line metastatic chemotherapy and their survival data. Between 2009 and 2014, we reviewed 118 patients with metastatic breast cancer. All the patients fulfilled our inclusion criteria. In all, 48% of patients were obese and 52% were non obese. There were no statistically significant differences between the two groups. For arms A and B, the median interval between initial cancer diagnosis and distant metastases development (distant metastases-free survival) was 5.8 versus 7.6 years, respectively (P value 0.04). Earlier visceral (liver and lung) metastases were observed in obese compared to non-obese women (P values were 0.05 and 0.04, respectively). The most commonly used chemotherapy was weekly paclitaxel. Our treatments showed significantly better treatment response and better survival results in non-obese women than in obese ones, who were premenopausal with performance state 2, pathological grade 3, and four or more positive lymph nodes.