An important study was just published in JAMA Oncology that applies to breast cancer (and likely other cancer types) survivors.
University of California, San Diego investigators found that breast cancer survivors, who reported consistently not eating for 13 hours or more (overnight), had a 36% lower risk of having a breast cancer recurrence and 21% lower risk of dying from their breast cancer.
- “Women’s Healthy Eating and Living” (WHEL) study
- 2413 women with early stage breast cancer
- No patients had diabetes at enrollment
- Ages 27 to 70 years at diagnosis
- Nightly fasting duration was estimated from 24-hour dietary recalls collected at baseline, year 1, and year 4
- Baseline sleep duration was self-reported
- Archived blood samples were used to assess concentrations of hemoglobin A1c (marker of blood sugar levels over 3 months) and C-reactive protein (marker for systemic inflammation)
The Study Results:
- After a 7.3 year follow-up period, there was a:
- 36% higher risk of breast cancer recurrence in those who did not fast for greater than 13 hours, at night
- 21% higher risk of dying from breast cancer (a trend, albeit not statistically significant) in those who did not fast for greater than 13 hours, at night
- 22% higher risk of death from any cause (a trend, albeit not statistically significant) in those who did not fast for greater than 13 hours, at night
- Higher risk of elevated HbA1c (blood sugar lab test)
- No difference in CRP (inflammation lab test)
The authors suggested that those patients who did not fast for greater than 13 hours, from dinner until breakfast, had a shorter sleep duration. We know that short sleep durations, at night (less than 7 hours), are linked with disruptions in the body’s natural circadian hormonal levels (mainly: cortisol and melatonin.) Chronic circadian dysfunction is linked to an increase in many cancers, likely due to subsequent insulin resistance, systemic inflammation, increased obesity, etc. Read more about sleep and cancer in our article, here.
Regardless of sleep duration, those who had higher blood sugar levels (higher HbA1c), were not as likely to be fasting for greater than 13 hours at night.
- This study found higher HbA1c levels in those patients who didn’t fast for 13+ hours. Read more about the link between sugar levels and cancer in our article, here.
Although this study did not find an increase in the systemic inflammation marker (CRP) in those who didn’t fast for 13+ hours, other studies have reported this
If your oncologist thinks that you are healthy enough to fast for 13+ hours during the night, this might be good strategy to reduce your caloric intake and reduce your blood sugar levels…and possibly improve cancer outcomes.
I strongly encourage patients to try to consistent get at least 6-7 hours of sleep, during the night, to reduce circadian hormonal disruptions linked with systemic inflammation, insulin resistance, weight gain and other cancer promoting physiological effects.