This randomized controlled trial investigates the effects of intermittent fasting and water-only fasting on gene expression, tumor markers, quality of life, and chemotherapy tolerance in breast cancer patients receiving chemotherapy. Breast cancer remains the most commonly diagnosed cancer worldwide, and while chemotherapy constitutes standard treatment, it is frequently accompanied by significant adverse effects including cachexia and immunosuppression. Fasting has emerged as a promising complementary approach that may enhance chemotherapy efficacy while protecting healthy cells from treatment-related toxicity. The study will enroll 60 female breast cancer patients from INOR, Abbottabad, who will be randomly assigned to one of four groups: conventional chemotherapy alone, chemotherapy combined with intermittent fasting (23:1 hour fasting to eating ratio) plus routine diet, chemotherapy combined with intermittent fasting plus ketogenic diet, or chemotherapy combined with water-only fasting for two weeks. Blood samples will be collected before and after interventions to assess tumor marker CA 15-3, CD4+ and CD8+ T cell counts, oxidative stress marker malondialdehyde, inflammatory markers including TNF-α and neutrophil-lymphocyte ratio, Glasgow Prognostic Score, and metabolic regulators AMPK and pyruvate dehydrogenase. Quality of life will be evaluated using the validated FACT-B questionnaire, while chemotherapy tolerance will be assessed through symptom severity surveys. The study hypothesizes that combining fasting regimens with standard chemotherapy will enhance anti-tumor effects, improve immune surveillance mechanisms, and ultimately contribute to better prognostic outcomes in breast cancer patients.