Breast cancer remains the most prevalent malignancy among women worldwide, with lifestyle factors such as diet, physical activity, and body weight playing pivotal roles in its prevention, progression, and survivorship. This systematic review synthesizes evidence from epidemiological studies, clinical trials, and meta-analyses published between 2005 and 2025 to evaluate the impact of nutritional interventions and healthy behaviors on breast cancer risk, recurrence, and mortality. A comprehensive literature search across major databases identified over 50 high-quality studies, including randomized controlled trials and cohort analyses. Key findings indicate that adherence to healthy dietary patterns—characterized by high intake of vegetables, fruits, whole grains, and omega-3 fatty acids, while limiting red/processed meats, saturated fats, and alcohol—reduces breast cancer incidence by 20-30% and improves survival rates by mitigating oxidative stress and inflammation. Obesity, particularly postmenopausal, emerges as a strong prognostic factor, increasing recurrence risk by up to 40%, whereas weight management through combined diet and exercise interventions enhances chemotherapy tolerance and quality of life. Physical activity, even at moderate levels, is associated with a 25-35% reduction in mortality, potentially via improved insulin sensitivity and immune function. Specific nutrients like vitamin D and antioxidants show promise in adjuvant therapy, alleviating treatment side effects and supporting estrogen receptor-positive subtypes. Despite these benefits, inconsistencies arise from study heterogeneity, including variations in menopausal status and tumor molecular profiles. Future research should prioritize personalized nutrition strategies and long-term trials to optimize outcomes. Overall, integrating evidence-based dietary and lifestyle modifications into clinical guidelines could significantly lower breast cancer burden and empower survivors. Keywords :- Breast cancer, Chemotherapy, Nutritional interventions, Lifestyle interventions ,Dietary supplements , Oral nutritional supplements.