Longer Nightly Fasting Reduced Risk for Breast Cancer Recurrence

Researchers have found a link between the duration of fasting at night and the risk for breast cancer recurrence among women with early-stage breast cancer. According to a study published in JAMA Oncology, fasting less than 13 hours per night was associated with an almost 40% increased risk for breast cancer recurrence compared with fasting more than 13 hours per night.

“In this cohort of patients with early-stage breast cancer, a longer nightly fasting interval was also associated with significantly lower concentrations of HbA1c and longer sleep duration,” wrote researchers led by Catherine R. Marinac, BA, of the University of California, San Diego Moores Cancer Center, and colleagues. “Given the associations of nightly fasting with glycemic control and sleep, we hypothesize that interventions to prolong the nightly fasting interval could potentially reduce the risk of type 2 diabetes, cardiovascular disease, and other cancers.”

According to background information in the study, rodent studies have suggested that prolonged fasting during sleep can protect mice fed a high-fat diet against abnormal glucose metabolism, inflammation, and weight gain, all of which have been linked with poor cancer outcomes.

In this study, the researchers examined whether the duration of nightly fasting predicted breast cancer prognosis. The researchers used data from the Women’s Health Eating and Living study on 2,413 women with breast cancer but no diabetes aged 27 to 70 at diagnosis. Duration of nightly fasting was estimated from 24-hour dietary recalls collected from the participants at baseline, year 1 and year 4. The primary endpoint was the number of invasive breast cancer recurrences or new primary breast cancer tumors.

On average patients reported fasting for 12.5 hours per night. Those patients who reported fasting less than 13 hours a night were more likely to have a college education, have a higher caloric intake, have more eating episodes, and to have eaten after 8 pm.

Women who fasted less than 13 hours a night had a 36% increased risk for breast cancer recurrence (hazard ratio, 1.36 [95% CI, 1.05–1.76]). However, this shorter fasting duration was not associated with an increased risk for breast cancer–specific or overall mortality.

The researchers found that each 2-hour increase in nightly fasting duration was associated with significantly lower levels of HbA1c, and a longer duration of nighttime sleep.

“Consuming food at abnormal times (eg, late at night) can result in misalignment of circadian rhythms, which can influence sleep patterns and disrupt metabolic factors, such as glucoregulation,” the researchers wrote. “Notably, circadian misalignment has been linked to increased risk of many cancers, as evidenced by the well-documented association between shift work and increased risk of breast cancer.”

The researchers pointed out that the use of self-reported timing of food intake and sleep duration was a weakness in this study because they may be subject to bias and recall error.

“Our study introduces a novel dietary intervention strategy and indicates that prolonging the length of the nightly fasting interval could be a simple and feasible strategy to reduce breast cancer recurrence,” the researchers wrote. “Randomized trials are needed to adequately test whether prolonging the nightly fasting interval can reduce the risk of chronic disease.”