Prolonged Fasting (48–72h) — Chemotherapy Sensitisation
Prolonged fasting of 48–72 hours before and after chemotherapy is the most clinically studied fasting protocol in oncology, pioneered by Dr. Valter Longo at USC. The mechanism — called Differential Stress Resistance (DSR) — exploits a fundamental difference between cancer cells and normal cells: normal cells downregulate growth and enter a protective mode during fasting, while cancer cells (locked into perpetual growth signalling via oncogene activation) cannot. This renders normal cells more resistant to chemo toxicity and cancer cells more sensitive. Clinical trials in breast, ovarian, and prostate cancer show reduced chemotherapy side effects and preliminary evidence of improved tumour response.
Mechanism of Action
During 48–72h fasting, normal cells shift into a 'maintenance mode': they downregulate IGF-1 signalling, reduce mTOR activity, activate AMPK, and reduce reactive oxygen species (ROS) production. Cancer cells — driven by constitutively active oncogenes (RAS, PI3K, AKT) — cannot make this shift. They continue to produce ROS and remain metabolically active during the chemo assault. The result: chemotherapy disproportionately harms cancer cells while normal cells are shielded. This is Differential Stress Resistance (DSR), also called Short-Term Starvation (STS).
Cancer Types Studied
Protocols & Dosing
Longo Pre-Chemo Protocol (72h)
Begin fasting 48–72 hours before chemotherapy infusion. Water, plain herbal tea, and black coffee only. Break the fast 24 hours after the infusion completes. Discuss caloric needs and hydration with your oncologist.
Fasting Mimicking Diet (FMD)
A 5-day low-calorie, low-protein, low-carb diet (300–1100 kcal/day) that mimics fasting biochemically without complete abstinence. Developed by Valter Longo. Commercial version: ProLon kit. Easier for patients who struggle with complete fasting. Clinical trial evidence available.
24-Hour Pre-Chemo Fast
Shorter version for patients who cannot tolerate longer fasts. Fast 24 hours before infusion, resume eating 12–24 hours after. Less studied than 48–72h but may still confer benefit via DSR mechanism.
NIH / PubMed Research
Links open on PubMed (National Library of Medicine). Research is ongoing — results may not reflect clinical use.
Cautions & Contraindications
- MUST be done under oncologist supervision — not appropriate for all chemotherapy regimens
- Do not attempt if underweight (BMI < 18.5), malnourished, or with cachexia
- Electrolyte monitoring recommended for fasts over 48 hours
- Ensure adequate hydration — 2–3 litres of water daily during fast
- Not suitable during radiation therapy or surgery recovery
- Diabetics and those on blood pressure medication need medical supervision
- Break the fast gradually — start with soup or light broth
Informational only. Not medical advice. Consult your oncologist before starting any alternative or integrative therapy.