Nighttime Fasting May Help Reduce Breast Cancer Risk

Catherine Marinac

New research reported at the AACR Annual Meeting has found that decreasing the number of hours spent eating each day and increasing the number of hours spent fasting overnight may reduce a woman’s risk of developing breast cancer.

Previous preclinical studies have suggested these steps may improve metabolic parameters and reduce the risk of developing a number of chronic diseases, including cancer; however, no human studies had explored the potential impact of this type of fasting schedule on cancer risk factors such as hyperglycemia, which is a possible facilitator of neoplastic proliferation.

“We found that women who fasted for longer periods of time overnight had significantly better control over blood glucose concentrations, and these effects were independent of how much they ate,” lead author Catherine Marinac, doctoral candidate in public health at the University of California, San Diego, said in a statement.

“This finding is relevant to cancer research because people who have poor glucose control are more likely to develop certain types of cancer, and it is hypothesized that high concentrations of circulating glucose may fuel cancer growth and progression.”

For the study, researchers looked at possible associations between the duration of nighttime fasting and glycemic control biomarkers associated with increased breast cancer risk in a population-based sample of women in the 2009-2010 US National Health and Nutrition Examination Survey.

Women included in the study were a median age of 47 years. Data on HbA1c levels over the previous 2 to 3 months were available for 2212 women, and data on 2-hour postprandial blood sugar were available for 1066 women. The women fasted for approximately 12.4 hours per night.

The results showed that for each 3-hour increase in nighttime fasting, women had a 4% lower 2-hour postprandial blood sugar measurement and a nonsignificant 0.4 unit decrease in HbA1c.

Each 3-hour increase in nighttime fasting was also associated with about 20% reduced odds of having elevated HbA1c and nonsignificantly reduced odds of an evaluated 2-hour postprandial blood sugar measurement.

“Our group is hoping to gain funding for a large-scale trial to confirm these findings,” Marinac said. “If these findings are reproduced, it would mean that increasing the duration of overnight fasting could be a novel strategy to reduce the risk for developing breast cancer.”

“This is a simple dietary change that we believe most women can understand and adopt, and it may have a big impact on public health.”

Marinac CR, Natarajan L, Sears DD, et al. Prolonged nightly fasting and breast cancer risk: findings from NHANES (2009-2010). Presented at: AACR Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA. Abstract 1234.