94 A recent comprehensive systematic review and meta-analysis has highlighted the significant impact of body mass index (BMI) on breast cancer prognosis. This study, conducted by Nikolaos Tzenios and colleagues, consolidates data from 46 studies, encompassing nearly 300,000 patients, to assess the correlation between BMI and breast cancer outcomes. The findings were published in the journal Medicine. The findings indicate a clear association between higher BMI and increased breast cancer risk. Obesity, defined as a BMI of 30 or higher, was found to be significantly higher in breast cancer patients compared to control groups. This elevated risk was consistent across various populations and study designs included in the meta-analysis. The study particularly emphasised that obesity not only increases the incidence of breast cancer but also adversely affects survival rates and overall prognosis. The analysis showed that obese patients tend to have more aggressive tumour characteristics and are more likely to present with advanced-stage disease at diagnosis. This trend underscores the critical need for targeted interventions and weight management strategies to mitigate breast cancer risk in obese women. Several mechanisms have been proposed to explain the link between obesity and breast cancer. One key factor is the higher levels of estrogen found in obese postmenopausal women due to the aromatisation of androgens in adipose tissue. Elevated estrogen levels can promote the development and progression of hormone-receptor-positive breast cancers. Additionally, obesity is associated with chronic inflammation, insulin resistance, and alterations in adipokines and cytokines, all of which can contribute to carcinogenesis and tumour growth. The study also explored the impact of BMI on various breast cancer subtypes. For instance, obesity was found to significantly influence the prognosis of HER2-positive and triple-negative breast cancer (TNBC) patients. These subtypes are known for their aggressive behaviour and poorer outcomes, and obesity appears to exacerbate these challenges. In contrast, the relationship between BMI and hormone receptor-positive (HR+) breast cancers was less pronounced. But even in HR+ cancers, higher BMI was still associated with worse outcomes compared to patients with normal BMI. Interestingly, the study noted a nuanced relationship between being overweight (BMI of 25 to 29.9) and breast cancer risk. Unlike obesity, being overweight did not show a significant association with increased breast cancer risk across all included studies. This finding suggests that while extreme obesity is a clear risk factor, the impact of moderate overweight status may vary depending on other individual and environmental factors. The study’s authors advocate for the implementation of effective weight management programmes as a critical component of breast cancer prevention strategies. Given the robust association between obesity and poor breast cancer outcomes, promoting healthy body weight through diet, exercise, and behavioural interventions could substantially reduce breast cancer incidence and improve survival rates. The findings support the need for personalised treatment approaches that consider BMI as a factor in clinical decision-making. For example, obese breast cancer patients might benefit from more aggressive screening protocols and tailored therapeutic regimens to address the heightened risk and complexity of their disease.