Women with breast cancer are a growing population due to improved screening and treatment. It has been described that chemotherapy can negatively affect patients’ metabolism. The aim of this study is to assess weight gain during chemotherapy treatment in an interim analysis on an ongoing prospective cohort of women with early breast cancer. To help untangle the many possible reasons for weight change, we examine blood tests, Patient-Reported Outcomes (PROs), and bone mineral density (BMD). We find that the 38 women that have measurements taken after chemotherapy have an average weight gain of 1.2 kg although not significant. Together with this, there is a significant drop in HDL cholesterol, an increase in triglycerides, and a non-significant tendency towards decreased insulin sensitivity. PROs show that although the women experience more pain and fatigue, they have higher activity levels. BMD is at an expected level according to age. All in all, we see an increased focus on physical activity and nutrition, leading to less severe metabolic changes as previously reported. However, even though more measures are taken, we still see an overall negative metabolic impact with unknown long-term implications.