Eating frequency, timing of meals, and sleep duration before and after a randomized controlled weight loss trial for breast cancer survivors.

Purpose: To examine eating frequency, timing of meals, and sleep duration before and after a weight loss intervention for breast cancer survivors.

Methods: Female breast cancer survivors (n = 159; 55 ± 9 years; 31.4 ± 5.0 kg/m²; stage I-III, median [IQR] 9.5 [5.5] months post-diagnosis) participated in a randomized controlled trial of a 12-month weight loss intervention versus usual care. Eating frequency, proportion of daily calories consumed after 5 PM, eating after 8 PM, nightly fasting duration, and sleep duration were estimated and categorized based on existing associations with factors influencing breast cancer prognosis and breast cancer outcomes. These behaviors at baseline were compared to women from an Australian national survey with similar age and BMI range. Mixed-effects linear regression models were used to examine the changes in health behaviors from baseline to 18 months between intervention and usual care groups.

Results: Before the trial, eating after 8 PM (67%) was higher, and short nightly fasting duration (< 13 h, 83%) and long sleep duration (> 9 h/day, 26%) were marginally higher, in breast cancer survivors than women in the national survey (52%, 75%, and 17%, respectively). "Less optimal" eating behaviors and sleep duration tended to co-occur. Behaviors remained unchanged over the 18-month follow-up, irrespective of the study group (p > 0.05; Cohen's effect sizes < 0.3).

Conclusions: Later timing of eating and long sleep duration were prevalent in breast cancer survivors and continued following a weight loss intervention.

Implications for cancer survivors: Future multi-behavior interventions in breast cancer survivors should consider specific messages to target eating timing behaviors and sleep.