Prolonged Nightly Fasting and Breast Cancer Prognosis

Authors: Marinac, C.R., Nelson, S.H., et al.

Source: JAMA Oncol. doi:10.1001/jamaoncol.2016.0164

www.ncbi.nlm.nih.gov/pubmed/27032109

The authors of this paper noted that there is data in animals and humans to suggest that prolonged nightly fasting (a continuous period of not eating, which includes sleeping) may reduce breast cancer risk and improve breast cancer outcomes.

A total of 2,413 women, all with histories of early breast cancer, were studied. These individuals were called on random days during a three week period at the time of enrollment, one year after that and then four years later. The women were asked to note the number of hours between the first and last eating episodes of the previous 24-hour period. This total was subtracted from 24 to get a nightly fasting duration.

Mean follow up was 7.3 years, during which time episodes of breast cancer recurrence were observed. The mean nighttime fasting duration was 12.5 hours. The investigators noted that fasting fewer than 13 hours a night was associated with a 36% higher risk of breast cancer recurrence. However, the length of nighttime fasting did not affect breast cancer-related death or death due to all causes.

The group evaluated the association between nighttime fasting and body mass index (BMI), hemoglobin A1c (HbA1c) and C-reactive protein (CRP). Each of these parameters is suspected to link nightly fasting duration with breast cancer prognosis. The levels of HbA1c decreased as the length of nighttime fasting increased. Length of nighttime fasting was not associated with BMI or CRP.

The investigators concluded that a nighttime fasting length of at least 13 hours was associated with a lower rate of breast cancer recurrence. The mechanisms of action may include a direct effect on HbA1c levels, which modulate glycemic (blood sugar) control. Further study into the effects of prolonged nighttime fasting on breast cancer, diabetes and other diseases is warranted.