Intermittent Fasting (16:8 / Time-Restricted Eating)
Intermittent Fasting (IF) involves cycling between defined eating and fasting windows daily. The most studied pattern is 16:8 — 16 hours fasting, 8 hours eating. A landmark study in breast cancer survivors (WHEL study) found that a 13-hour overnight fast reduced recurrence risk by 36%. IF lowers insulin, IGF-1, and inflammatory markers — all known cancer promoters — while activating autophagy (cellular clean-up) and shifting metabolism away from glycolysis towards fat oxidation.
Mechanism of Action
During fasting, falling insulin and glucose levels activate AMPK (a cellular energy sensor) and inhibit mTOR — a master regulator of cell growth and proliferation. mTOR inhibition induces autophagy, which clears damaged organelles and may eliminate pre-cancerous cells. Reduced IGF-1 lowers cellular proliferation signals. Ketone bodies produced during fasting are metabolised efficiently by normal cells but poorly by many cancer cell types. Additionally, IF reduces circulating oestrogen in overweight women, directly addressing a key breast cancer driver.
Cancer Types Studied
Protocols & Dosing
16:8 Daily Fast
Fast for 16 consecutive hours (including sleep). Eat within an 8-hour window (e.g. 10am–6pm). Drink water, black coffee, or plain herbal tea during the fasting window. Start with 12 hours and extend weekly.
13-Hour Overnight Fast (WHEL Protocol)
Finish dinner by 7pm, breakfast no earlier than 8am. Simple, evidence-backed, and comfortable for most people during cancer treatment. Minimum effective dose from the WHEL breast cancer study.
5:2 Protocol
Eat normally 5 days per week. On 2 non-consecutive days, restrict calories to 500–600 kcal (not zero). Easier for those who struggle with daily fasting. Evidence similar to 16:8 for metabolic markers.
NIH / PubMed Research
Links open on PubMed (National Library of Medicine). Research is ongoing — results may not reflect clinical use.
Cautions & Contraindications
- Do NOT fast if underweight, malnourished, or losing weight during treatment — caloric needs take priority
- Discuss with oncologist before starting — some chemotherapy regimens require food intake with medication
- Avoid if history of eating disorders
- Diabetics on insulin or sulphonylureas must monitor blood glucose carefully — hypoglycaemia risk
- Not appropriate during radiation therapy without dietitian guidance
Informational only. Not medical advice. Consult your oncologist before starting any alternative or integrative therapy.