Medical synopsis: Nightly fasting may assist breast cancer patients and other people with cancer

Design: A multi-site randomised clinical trial. Participants: The Women's Healthy Eating and Living (WHEL) study of patients with breast cancer. Data was collected from 2413 women with breast cancer but without diabetes mellitus, aged 27-70 years at diagnosis. A total of 2064 participants (85.5%) were Caucasian with 1335 (55.3%) college educated. Intervention: Dietary analysis including timing of consumption at baseline, year 1 and year 4. A 24-h dietary recall collected by telephone on random days during a 3-week period, stratified for weekends vs weekdays. Nightly fasting duration was estimated by calculating the elapsed hours between the first and last eating episode for each day and subtracting that time from 24 h. Potential confounders were identified including daily intake (kilocalories), eating episodes per day and eating after 8 pm. Comparator: No comparator was used in this study. Major outcomes: Participants reported a mean (SD) nightly fasting duration of 12.5 h and 4.4 eating episodes per day. One-third of the sample consumed 25 kcal or more after 8 pm. A short nightly fasting duration (< 13 h per night) was significantly associated with college education, a lower BMI, shorter sleep duration, higher self-reported kilocalorie intake, more eating episodes, and eating after 8 pm. A short nightly fast (< 13 h) was significantly associated with an increased risk for breast cancer recurrence (36% higher risk). Each 2-h increase in nightly fasting duration was statistically significant for lower HbA1c level (0.37 mmol/ mol lower) and more hours of sleep per night. Nightly fasting was not associated with BMI or CRP concentrations. Eating after 8 pm was significantly associated with increased higher CRP and BMI. Settings: The United States of America: Clinical sites included University of California, San Diego; University of California, Davis; Stanford University; Kaiser Permanente, Northern California; M. D. Anderson Cancer Centre; Arizona Cancer Centre; and Kaiser Permanente Center for Health Research. Conclusion: Prolonged nightly fasting duration (13 h or more), may be a simple, non-pharmacologic strategy for reducing the risk of breast cancer recurrence. In addition, improvements in gluco-regulation and sleep may be mechanisms of action linked with nightly fasting and breast cancer prognosis. (C) 2016 Elsevier Ltd. All rights reserved.