Systematic reviewindependent cross-checkabstract only checked★ key study I-INTA-10 in-depth review
Does intermittent fasting help during chemotherapy?
Impact of intermittent fasting on patients with cancer undergoing chemotherapy and/or targeted therapies: a systematic review of the literature.
Overview
Maes J et al.. Supportive care in cancer : official journal of the Multinational Association of Supportive Care in Cancer 2025 · PMID 40970988 · DOI 10.1007/s00520-025-09907-7
Nine small studies found fasting feasible and safe under supervision but showed no proven effect on treatment results or side effects.
Does the study support the specific claim? No · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Intermittent fasting during cancer therapy
- How was the study done?
Systematic review
- How many people, animals or samples were studied?
9 studies, 354 patients
- What was actually found?
Safe and feasible; no demonstrated effect on outcomes
- How large was the observed effect?
Not pooled
- What do the results mean in everyday life?
Fasting is not a proven cancer treatment
- What are the study's limitations?
Few small studies
- What does it say about Elawady's specific claim?
Contradicts 'treating cancer with fasting'
- Do the results apply to Germany and Europe?
High
- What can explicitly not be concluded from this study?
Effects of fasting without standard treatment (not studied)
Scientific in-depth review
1. Full reference
- Authors
- Maes J et al.
- Journal
- Supportive care in cancer : official journal of the Multinational Association of Supportive Care in Cancer
- Year
- 2025
- Identifier
- PMID 40970988 DOI 10.1007/s00520-025-09907-7
- Verification
- verified – PubMed efetch 2026-10-25
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
Safety, feasibility, tolerability and metabolic effects of intermittent fasting in patients receiving chemotherapy and/or targeted therapy
3. Study design and population
- Study design
- Systematic review – Systematic review
- Population
Cancer patients undergoing chemotherapy or targeted therapy (mostly breast cancer)
- Country
Multinational
- Period
1990 to March 2025
- Sample size
9 studies, 354 patients (258 with breast cancer)
- Inclusion and exclusion criteria
Studies of intermittent fasting during chemotherapy/targeted therapy
4. Methods and endpoints
- Exposure / intervention
Intermittent fasting
- Comparator
Usual diet (varies)
- Endpoints
Treatment efficacy, toxicity, quality of life, fasting tolerance, metabolic markers
- Statistical methods
Narrative synthesis; risk-of-bias assessment
5. Actual results
- Results
Safety and feasibility confirmed, but no impact on treatment outcomes or chemotherapy-related toxicities demonstrated. Consistent trend of lower insulin and IGF-1 and higher erythrocyte levels with fasting. Three studies reported no difference in body weight/BMI. Risk of bias low to moderate.
- Absolute risks
not reported
- Authors' conclusion
Intermittent fasting appears safe and feasible, but evidence is insufficient to conclude on treatment effectiveness or side effects; larger RCTs needed.
6. Strengths
- Recent systematic search
- Risk-of-bias assessment
7. Weaknesses
- Few, small studies
- Mostly breast cancer
- Short-term fasting regimens, not alternate-day fasting as sole therapy
8. Risk of bias
- Orienting tool
- AMSTAR 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Simplified; small evidence base.
9. Assessment of the statistical interpretation
Absence of demonstrated benefit with low power; not proof of no effect.
10. Relevance to the specific claim
Summarises all clinical data on intermittent fasting during cancer therapy.
11. Independent contrary findings
DIRECT trial (I-INTA-08) signal on response.
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
Fasting during cancer therapy is a research question, not an established treatment.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | low |
| Directness | indirect |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Large RCTs with survival endpoints.
15. Linked fact checks
- In his practice he treats cancer with fasting (fasting every other day) and by reducing solid foods; he himself can go for days without food, on sugar-cane juice only. – Studies contradicting or limiting the claim