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All,

 

I personally don't do extended fasts except on rare occasions (like my last colonoscopy, when I had to go 5 days without food to clear out my colon for imaging). But I do eat in a limited time window, and fast for most of the day and night, both for convenience, and because I believe it to be healthy for a number of reasons (reduced glucose / insulin exposure, increased autophagy, etc). It looks like we can add 'reducing breast cancer recurrence' to the list of benefits of an extended overnight fast, according to a new study [1] in this month's issue of JAMA (popular press story).

 

In a study of 2400 breast cancer survivors, researchers found that waiting more than 13 hours between her last meal or snack in the evening and her first meal in the morning resulted in a 36% reduction in a woman's risk of breast cancer recurrence relative to fasting for less than 13 hours. The women who fasted longer had better markers of glucose control (HbA1C) and increased sleep duration. The researchers think these benefits may have been at least partly responsible for the reduction in breast cancer recurrence.

 

--Dean

 

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[1] JAMA Oncol. 2016 Mar 31. doi: 10.1001/jamaoncol.2016.0164. [Epub ahead of print]

 
Prolonged Nightly Fasting and Breast Cancer Prognosis.
 
Marinac CR(1), Nelson SH(2), Breen CI(3), Hartman SJ(4), Natarajan L(4), Pierce
JP(4), Flatt SW(3), Sears DD(5), Patterson RE(4).
 
 
Importance: Rodent studies demonstrate that prolonged fasting during the sleep
phase positively influences carcinogenesis and metabolic processes that are
putatively associated with risk and prognosis of breast cancer. To our knowledge,
no studies in humans have examined nightly fasting duration and cancer outcomes.
Objective: To investigate whether duration of nightly fasting predicted
recurrence and mortality among women with early-stage breast cancer and, if so,
whether it was associated with risk factors for poor outcomes, including
glucoregulation (hemoglobin A1c), chronic inflammation (C-reactive protein),
obesity, and sleep.
Design, Setting, and Participants: Data were collected from 2413 women with
breast cancer but without diabetes mellitus who were aged 27 to 70 years at
diagnosis and participated in the prospective Women's Healthy Eating and Living
study between March 1, 1995, and May 3, 2007. Data analysis was conducted from
May 18 to October 5, 2015.
Exposures: Nightly fasting duration was estimated from 24-hour dietary recalls
collected at baseline, year 1, and year 4.
Main Outcomes and Measures: Clinical outcomes were invasive breast cancer
recurrence and new primary breast tumors during a mean of 7.3 years of study
follow-up as well as death from breast cancer or any cause during a mean of 11.4 
years of surveillance. Baseline sleep duration was self-reported, and archived
blood samples were used to assess concentrations of hemoglobin A1c and C-reactive
protein.
Results: The cohort of 2413 women (mean [sD] age, 52.4 [8.9] years) reported a
mean (SD) fasting duration of 12.5 (1.7) hours per night. In repeated-measures
Cox proportional hazards regression models, fasting less than 13 hours per night 
(lower 2 tertiles of nightly fasting distribution) was associated with an
increase in the risk of breast cancer recurrence compared with fasting 13 or more
hours per night (hazard ratio, 1.36; 95% CI, 1.05-1.76). Nightly fasting less
than 13 hours was not associated with a statistically significant higher risk of 
breast cancer mortality (hazard ratio, 1.21; 95% CI, 0.91-1.60) or a
statistically significant higher risk of all-cause mortality (hazard ratio, 1.22;
95% CI, 0.95-1.56). In multivariable linear regression models, each 2-hour
increase in the nightly fasting duration was associated with significantly lower 
hemoglobin A1c levels (β = -0.37; 95% CI, -0.72 to -0.01) and a longer duration
of nighttime sleep (β = 0.20; 95% CI, 0.14-0.26).
Conclusions and Relevance: Prolonging the length of the nightly fasting interval 
may be a simple, nonpharmacologic strategy for reducing the risk of breast cancer
recurrence. Improvements in glucoregulation and sleep may be mechanisms linking
nightly fasting with breast cancer prognosis.
 
PMID: 27032109

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