Prolonged nightly fasting may reduce the risk of recurrence for patients with breast cancer, a study published in JAMA Oncology has shown.1

Because rodent studies have demonstrated that prolonged fasting during the sleep phase positively impacts carcinogenesis and metabolic processes that are known to be associated with risk and prognosis of breast cancer, researchers sought to investigate whether duration of nightly fasting predicted recurrence and mortality among women with early stage breast cancer.

For the study, researchers analyzed data from 2413 women with breast cancer but without diabetes who participated in the Women’s Healthy Eating and Living study. Patients were eligible for inclusion if they were age 27 years to 70 years at the time of diagnosis.

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To estimate patients’ nightly fasting duration, 24-hour dietary recalls were collected at baseline, year 1, and year 4. Results showed that the average fasting duration was 12.5 hours per night.

Researchers found that fasting less than 13 hours per night was associated with an increased risk of breast cancer recurrence compared with fasting 13 hours or more per night (HR, 1.36; 95% CI: 1.05-1.76); however, there was no statistically significant difference in breast cancer mortality or all-cause mortality between nightly fasting less than 13 hours and fasting 13 hours or more.

Further, the study demonstrated that each 2-hour increase in the nightly fasting duration was associated with significantly lower hemoglobin A1C levels and a longer duration of nighttime sleep.

The findings suggest that extending the length of the nightly fasting interval may be a simple, nonpharmacologic strategy for reducing the risk of breast cancer recurrence. Interventions that prolong the nightly fasting interval could potentially decrease the risk for developing type 2 diabetes, cardiovascular disease, and other cancers.


1. 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.