Posted on: October 7, 2025
A 2016 study published in JAMA Oncology showed breast cancer survivors who fasted for 13 hours per night had a 36% reduced chance of recurrence than breast cancer survivors who did not fast. The study appears scientifically accurate, as it followed 2413 women for 7 years, while breast cancer or any cause mortality was tracked for 11 years.
Based on their findings, the investigators concluded that simply extending the length of the nightly fasting period could be a medication-free strategy to reduce the risk of breast cancer recurrence. As a result of this study, our advice to patients in clinic is to finish dinner at 5 or 6 pm and have breakfast at 7 am with no snacks in between.
The benefit may be related to improved sleep and improved glucose regulation. It may be that longer fasting lowers both blood sugar and/or insulin production, two actions that may limit growth of breast cancer cells.
Longer fasting was associated with long sleep duration. Late-night eating disrupts circadian rhythms. Eva Schernhammer’s multiple studies of night-shift workers have produced convincing evidence that circadian misalignment is linked with increased cancer risk, including increased risk of breast cancer.
Because this study suggests a nearly 40% shift in cancer recurrence rates, longer nighttime fasts may have considerable value to breast cancer survivors, but also to those who are at higher risk of cancers in general (family history, night shift workers, etc).
"Eat an early dinner and a late breakfast."
References:
Schor, J. Nightly Fasting Improves Breast Cancer Prognosis. Natural Medicine Journal. 2016;8(9) http://www.naturalmedicinejournal.com/journal/2016-09/nightly-fasting-improves-breast-cancer-prognosis
Marinac CR, Nelson SH, Breen CI, et al. Prolonged nightly fasting and breast cancer prognosis [published online ahead of print March 31, 2016]. JAMA Oncol. doi: 10.1001/jamaoncol.2016.0164.