Fasting and Fasting-Mimicking Diets as Adjunctive Strategies in Cancer Therapy: Mechanisms, Evidence, and Clinical Implications

Background: Cancer remains a leading cause of global morbidity and mortality. Although conventional therapies such as chemotherapy, radiotherapy, and immunotherapy improve survival, their effectiveness is often limited by resistance and toxicity. Fasting and fasting-mimicking diets (FMDs) have emerged as potential adjunctive interventions due to their effects on cellular metabolism, stress responses, and tumor-host interactions. Aim: To critically evaluate the biological rationale, molecular mechanisms, and clinical evidence supporting fasting and FMDs as adjuncts in cancer therapy. Methods: A comprehensive literature review was conducted using PubMed, PubMed Central, and Google Scholar to identify relevant preclinical and clinical studies on fasting, caloric restriction, and FMDs in cancer. Results: Preclinical studies demonstrate that fasting induces metabolic and oxidative stress, selectively sensitizing cancer cells while protecting normal cells. Early-phase clinical trials suggest that fasting and FMDs are safe, feasible, and capable of influencing metabolism and immune responses, with potential improvements in treatment tolerance and efficacy. However, these studies are limited by small sample sizes and heterogeneous designs. Conclusion: Fasting and FMDs represent promising adjunctive strategies in cancer therapy. While mechanistic data and preliminary clinical findings are encouraging, larger, well-designed trials are required to confirm their efficacy, safety, and long-term benefits.