Fasting and cancer: what the research really says
Hello my lovely community,
If there's one question that comes up at almost every event I table and in almost every first session with a client, it's this:
"Should I be fasting?"
Sometimes it comes from a friend who swears by it. Sometimes it's a headline about fasting "starving" cancer cells. And sometimes it's simply a hope that there's one more thing you can do.
I understand that hope deeply. So I spent some time with the research, on both the conventional and integrative sides, and wrote a full blog post on it this week.
Here's the heart of it.
Fasting is not a cancer treatment, and it isn't safe for everyone.
If you're losing weight without trying, have a low appetite, are dealing with vomiting or diarrhea, take medication that lowers your blood sugar, or have any history of disordered eating, fasting is not the right tool for you right now. Your body's priority is nourishment.š ²
"Fasting" means very different things.
A consistent 12 to 13 hour overnight break (say, dinner done by 7 pm and breakfast at 7 or 8 am) is the gentlest and best-studied version. In one study of women with early-stage breast cancer, those who fasted fewer than 13 hours overnight had a higher risk of recurrence.Âł That's a link, not proof, but it's an encouraging one.
A multi-day fast or a fasting-mimicking diet is a very different thing. Early trials around chemotherapy are genuinely hopeful,â´ âľ but these belong only with your oncology team involved.
During treatment, fuel comes first.
Chemotherapy, radiation, and surgery ask a lot of your body. Getting enough protein and fat helps you protect your muscle, keep your strength up, and stay on schedule. For many of the people I work with, that matters more than any fasting window.
Cancer type matters.
Much of the strongest fasting research is in breast cancer, with some promising lab work in colorectal cancer and brain tumors. What fits one diagnosis may not fit another, which is exactly why this is such a personal decision.
--> Read the full blog post: Fasting and Cancer: What Helps, What Hurts, and When to Hold Off
In the post, I walk through the different types of fasting side by side, what the research shows for each, a simple way to start an overnight window, and the questions worth bringing to your next appointment.
If you're wondering whether fasting, or a completely different approach, makes sense for your body, I'd love to help you figure that out. Together, we can look at your diagnosis, your treatment, your appetite, your labs, and even your genetic tendencies, and build a plan that works alongside your oncology team.
Sending lots of love,
Michelle
Disclaimer
Š 2026 Mistletoe Nutrition and Wellness LLC
Disclaimer: The information shared in this newsletter is intended for inspirational and informational purposes only and is not a substitute for medical advice. Nothing in this newsletter is intended to diagnose, treat, prevent, or cure any disease. Consult with your healthcare provider before making any dietary, lifestyle, or supplement changes and do not forego or delay seeking medical attention based on the information shared in this newsletter. You acknowledge and agree that the results of any of our services, offerings, or products as described in a testimonial are not typical, are for illustrative purposes only, and cannot be guaranteed or assumed to be achievable by you. Please always consider your personal situation and do your own research.
Citations
- Arends J, Bachmann P, Baracos V, et al. ESPEN guidelines on nutrition in cancer patients. Clin Nutr. 2017;36(1):11-48. doi:10.1016/j.clnu.2016.07.015 https://pubmed.ncbi.nlm.nih.gov/27637832/
- Muscaritoli M, Arends J, Bachmann P, et al. ESPEN practical guideline: clinical nutrition in cancer. Clin Nutr. 2021;40(5):2898-2913. doi:10.1016/j.clnu.2021.02.005 https://doi.org/10.1016/j.clnu.2021.02.005
- Marinac CR, Nelson SH, Breen CI, et al. Prolonged nightly fasting and breast cancer prognosis. JAMA Oncol. 2016;2(8):1049-1055. doi:10.1001/jamaoncol.2016.0164 https://doi.org/10.1001/jamaoncol.2016.0164
- de Groot S, Lugtenberg RT, Cohen D, et al. Fasting mimicking diet as an adjunct to neoadjuvant chemotherapy for breast cancer in the multicentre randomized phase 2 DIRECT trial. Nat Commun. 2020;11(1):3083. doi:10.1038/s41467-020-16138-3 https://pubmed.ncbi.nlm.nih.gov/32576828/
- Vernieri C, FucĂ G, Ligorio F, et al. Fasting-mimicking diet is safe and reshapes metabolism and antitumor immunity in patients with cancer. Cancer Discov. 2022;12(1):90-107. doi:10.1158/2159-8290.CD-21-0030 https://aacrjournals.org/cancerdiscovery/article/12/1/90/675618/Fasting-Mimicking-Diet-Is-Safe-and-Reshapes
