Breast cancer survivors should skip late night snacking, study says

April 5, 2016 | by City of Hope

Breast cancer patients who indulge in midnight snacking might be doing harm to more than just their waistlines — they could be increasing their risk for reoccurrence, according to a new University of California, San Diego study published in JAMA Oncology.

Specifically, women whose usual “nightly fast” lasted less than 13 hours, had a 36 percent increased risk of having a reoccurrence of breast cancer within about seven years. In the study, recurrence was defined as cancer at the same site, or a new primary cancer.

Laboratory research has found that longer nighttime fasting can protect against high blood sugar levels, inflammation and weight gain. All are factors that have been linked with poor outcomes for cancer, according to the study’s authors.

“It's an interesting observation and it needs to be studied more,” Joanne Mortimer, M.D., director of City of Hope’s Women's Cancers Program, told HealthDay in an interview about the study. “I think sleep, diet and weight control are all kind of related.”

The University of California, San Diego research team looked at data from more than 2,400 women, aged 27 to 70, who had participated in the Women’s Healthy Eating and Living study between 1995 and 2007. All had been diagnosed with early-stage breast cancer, and the purpose of the study was to look at how diet and dietary habits affected outcomes.

The researchers found a link between lower fasting times – on average, the women fasted for 12.5 hours each night – and cancer recurrence. (An episode of eating was defined as consuming more than 25 calories.)

Ruth Patterson, Ph.D., one of the co-authors of the study, emphasized that the study found only an association. However, she added, "We have a lot of data suggesting that when people have bad sleep or shorter sleep duration, they may have a higher cancer risk."

"Evolutionary-wise, we are developed to eat when it is light, when we were out hunting and gathering," she said. "You should be eating when you are moving. When we go against these natural rhythms, it appears that your body clock is out of sync, and this can lead to poor metabolic health."

“Increasing the duration of overnight fasting could be a novel strategy to reduce the risk of developing breast cancer,” added Catherine Marinac, University of California, San Diego doctoral candidate and another of the paper’s authors. “This is a simple dietary change that we believe most women can understand and adopt. It may have a big impact on public health without requiring complicated counting of calories or nutrients.”

While the study is "provocative," Mortimer told HealthDay that it's too early to make a broad recommendation for breast cancer patients. She noted that many of her breast cancer patients report sleep problems. Those who fast longer and get better sleep may be less likely to develop metabolic syndrome, a cluster of conditions including high blood pressure, high blood glucose and low HDL or “good” cholesterol that can raise the risk of heart disease and other problems, she said.


Learn more about City of Hope's Breast Cancer Program. If you are looking for a second opinion or consultation about your treatment, request an appointment online or contact us at 800-826-HOPE. Please visit Making Your First Appointment for more information.

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