Impact of intermittent fasting on patients with cancer undergoing chemotherapy and/or targeted therapies: a systematic review of the literature.

PURPOSE

Intermittent fasting holds potential for improving cancer patient outcomes by promoting cancer cell death. Additionally, it depletes hepatic glycogen reserves, facilitating the release of fatty acids and ketones, which may enhance cancer cells sensitivity to chemotherapy and impede their proliferation. However, clinical data on fasting among cancer patients remain scarce. This systematic review intends to provide an overview of the impact of intermittent fasting on the safety, feasibility, tolerability, and metabolic effects of chemotherapy and targeted therapies in cancer patients.

METHODS

Articles were retrieved from 1990 to March 2025, employing a defined search equation. Established endpoints included cancer development, treatment efficacy, side effects related to chemotherapy and targeted therapies, quality of life, and fasting tolerance. Risk of bias was assessed, utilizing a validated assessment tool.

RESULTS

Among 1,725 articles, nine met our inclusion criteria. Risk of bias was low to moderate. These studies included patients predominantly with breast cancer (n = 258/354). Even though the safety and feasibility of intermittent fasting were confirmed, no impact on treatment outcomes and chemotherapy-related toxicities was demonstrated. However, a consistent trend emerged in reduced insulin and IGF-1 levels, along with increased erythrocyte levels among fasting patients. Three studies reported no significant difference in body weight and BMI.

CONCLUSION

Current evidence indicates that intermittent fasting is both safe and feasible. However, due to the lack of robust evidence, a definitive conclusion regarding the impact of intermittent fasting on treatment effectiveness and side effects related to chemotherapy and targeted therapies in cancer patients cannot be drawn. Larger randomized controlled trials are warranted to validate intermittent fasting as an adjunctive therapeutic approach.