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Women with early-stage breast cancer are less likely to have their cancer return if they fast for 13 hours every night, a new study finds.

Why it matters:

A growing body of evidence from rodent studies has shown that timing of meals influences disease risk. In humans, intermittent fasting has been shown to improve various risk factors for breast cancer  such as inflammation and blood sugar levels  but its effect on breast cancer itself hasn’t previously been studied.

The nitty gritty:

Researchers carried out periodic diet surveys of more than 2,000 women with early-stage breast cancer over a four-year period, asking participants to recall their last 24 hours of food intake. The scientists found that women who fasted fewer than 13 hours each night — meaning less than 13 hours between the last meal of the day and breakfast the next — had a 36 percent higher risk of breast cancer recurrence. This association held true independently of other dietary behaviors, such as number of calories consumed or frequency of meals. Women with shorter overnight fasting times, however, did not appear to have an increased risk of early death. The study was published in JAMA Oncology.


But keep in mind:

The researchers statistically controlled for things like demographics, sleep duration, and physical activity, but that is less ideal than actually randomly assigning people to either fast or not fast. More robust human studies, like randomized controlled trials, are needed, said lead investigator Catherine Marinac at University of California, San Diego.

Dr. Charles L. Shapiro, director of the Translational Breast Cancer Research at Mount Sinai, who was not involved in the study, agreed. Overnight fasting can’t hurt you, he said, but right now, “I can’t recommend it because I don’t have enough data that convinces me that this is a real effect.”


The bottom line:

Fasting for longer stretches at night may help reduce the likelihood of breast cancer returning. But the benefit of other strategies is even more strongly supported, including increasing physical activity and maintaining a healthy weight.