Frequency of Consuming Breakfast Meals and After-Dinner Snacks Is not Associated with Postmenopausal Breast Cancer Risk: Women's Health Initiative Observational Study.

BACKGROUND: There has been little investigation into how the timing of meals and eating occasions associates with postmenopausal breast cancer risk. OBJECTIVE: We examined the association between the frequency of consuming breakfast meals and after-dinner snacks with the risk for postmenopausal breast cancer. METHODS: A prospective analysis of 74,825 postmenopausal women aged 49 to 81 y from the Women's Health Initiative Observational Study cohort. Breakfast and after-dinner snack intake were assessed at year 1 examination. Risk for invasive and in situ breast cancer diagnosed before 28 February 2020 was modeled with multivariable Cox proportional hazards regression models according to breakfast and after-dinner snack consumption frequencies. The models were adjusted for age, self-identified race/ethnicity, education, income, physical activity, smoking, alcohol intake, diet quality score (Healthy Eating Index 2015), energy intake, diabetic status, hormone therapy, and BMI. RESULTS: During the follow-up period, 5313 participants were diagnosed with invasive breast cancer and 1197 participants with in situ breast cancer. Compared with participants who did not eat breakfast, those with daily breakfast consumption was not associated with invasive breast cancer (HR: 1.04; 95% CI: 0.9, 1.19) nor in situ (HR: 1.25; 95% CI: 0.91, 1.74) breast cancer. There were monotonic higher point estimates of in situ breast cancer for each higher category of breakfast intake from 0 to 7 times per week (P-trend = 0.04, Wald test). Compared with consumption of daily after-dinner snacks, avoidance of after-dinner snacks was not associated with invasive breast cancer (HR: 0.97; 95% CI: 0.87, 1.08) nor in situ (HR: 1.12; 95% CI: 0.89, 1.42) breast cancer. CONCLUSIONS: There was no association between intake frequency of breakfast meals or after-dinner snack habits and with risk of breast cancer in postmenopausal women.

A hypothetical intervention of the timing of dietary intake on weight and body composition after initial weight loss.

OBJECTIVE: This study estimated the effect of hypothetical interventions of higher and lower frequency of breakfast and post-dinner snack consumption (breakfast consumption 0-4 vs. 5-7 times/week and post-dinner snack consumption 0-2 vs. 3-7 times/week) on changes in body weight and composition over 18 months after a successful 6-month standard behavioral weight-loss program. METHODS: The study analyzed data from the Innovative Approaches to Diet, Exercise and Activity (IDEA) study. RESULTS: If all participants consumed a breakfast meal 5 to 7 times/week over 18 months, they would have regained 2.95 kg of body weight on average (95% CI: 2.01 to 3.96), which is 0.59 kg (95% CI: -0.86 to -0.32) lower than if all participants consumed breakfast 0 to 4 times/week. If all participants consumed a post-dinner snack 0 to 2 times/week, they would have regained 2.86 kg of body weight on average (95% CI: 0.99 to 5.25), which is 0.83 kg (95% CI: -1.06 to -0.59) lower than if all consumed a post-dinner snack 3 to 7 times/week. CONCLUSIONS: Regular breakfast consumption and minimizing post-dinner snacking may modestly mitigate weight and body fat regain over 18 months after initial weight loss.