SAN ANTONIO – Breast cancer survivors who typically didn’t eat for at least 13 hours overnight had a 36% reduction in the risk of breast cancer recurrence compared to those with a shorter duration of overnight fasting in a secondary analysis of the Women’s Healthy Eating and Living Study presented at the San Antonio Breast Cancer Symposium.
Catherine R. Marinac
“Prolonging the length of the nighttime fasting interval may be a simple nonpharmacologic strategy for reducing the risk of breast cancer recurrence as well as other chronic conditions with etiologic ties to breast cancer, like type 2 diabetes,” concluded to Catherine R. Marinac, a doctoral candidate in public health at the University of California, San Diego.
“A lot of dietary recommendations for cancer prevention really focus on what to eat in order to prevent or recover from breast cancer. For a lot of people that can be a really complicated recommendation, like ‘count your carbs, count your fat, don’t eat this/don’t eat that.’ We think timing of food intake in order to prolong the length of the nightly fasting interval can be a simple strategy most women can understand and adopt and that may reduce their risk of breast cancer,” she added.
The new results from the Women’s Healthy Eating and Living (WHEL) study are encouragingly consistent with the findings of earlier rodent studies demonstrating that intermittent fasting regimens aligned with the sleep cycle bring better glycemic control and protection against carcinogenesis, Ms. Marinac noted.
She presented an analysis of 2,413 nondiabetic breast cancer survivors who participated in the multicenter WHEL study and for whom multiple detailed 24-hour dietary recall records were obtained at baseline and 4 years of followup.
“The diets were very well characterized. We analyzed roughly 30,000 time-stamped dietary recalls,” she said in an interview.
During 7.3 years of follow-up, 390 women experienced recurrent breast cancer. Those in the top tertile for duration of overnight fasting, at 13 hours or longer, were 36% less likely to have a recurrence, according to a Cox proportionate hazard analysis and a multivariate linear regression analysis controlling for patient demographics; calorie consumption and other dietary variables; breast cancer stage, grade, and treatment; body mass index; comorbid conditions; and sleep duration.
During 11.4 years of follow-up, 329 subjects died of their breast cancer. All-cause mortality occurred in 420. Women with an overnight fasting duration of 13 hours or greater were 21% less likely to experience breast cancer mortality and 22% less likely to die of any cause. Neither trend achieved statistical significance.
Looking for potential mechanisms to explain the observed relationship between overnight fasting duration and breast cancer recurrence, Ms. Marinac and coinvestigators considered as evaluable possibilities systemic inflammation, glucoregulation, adiposity, and sleep duration.
C-reactive protein levels and body mass index proved to be unrelated to recurrence risk. However, glucoregulation and sleep duration were. Women with an overnight fasting length of at least 13 hours had a significantly lower glycated hemoglobin level and slept longer than those with a shorter overnight fast. The lower HbA1c seen in women who fasted for longer at night mimics an intriguing finding from the classic mouse studies that showed fasting is related to better glycemic control, she observed.
The WHEL study is sponsored by the National Cancer Institute, the University of California at San Diego, and a Ruth L. Kirschstein National Research Service Award. Ms. Marinac reported having no financial conflicts of interest.