(P15-015-23) Length of Overnight Fasting and Weight Change in the Cancer Prevention Study-3 Prospective Cohort

Objectives: Longer overnight fasting (ONF) is a potential strategy for weight control. While promising, the evidence from large population-based studies is limited. We examined the relationship of self-reported usual overnight fasting duration and three- and six-year weight change in the American Cancer Society’s Cancer Prevention Study-3 (CPS-3) cohort.

Methods: Adult men and women were enrolled in CPS-3 between 2006-2013 in 36 US states, the District of Columbia and Puerto Rico. 134,779 participants returned the 2015, 2018, and 2021 surveys; the 2015 survey contained a validated meal timing and frequency grid. Participants also completed questions on usual sleep hours. Three- and six-year weight change was calculated by subtracting body weight reported in 2015 from that reported in 2018 and 2021, respectively.

Results: After exclusions, including for missing meal timing grid and BMI, 105,016 men and women comprised the analytic cohort. Those who reported ≥13 h of ONF (vs 10- < 11 h) had lower baseline reported energy intake (1,789 vs 2,063 kcal/d), longer average sleep duration (8.29 vs 7.29 h), were more often female, less often non-Hispanic White, and reported lower household income and education. They were also less likely to be married, or to work full time and more likely to be ever smokers and report heavier alcohol drinking ( >2 drinks/d). There was no association of ONF with three-year weight change. However, those with longer ONF duration lost a small amount of weight (in kg) over six years (multivariable-adjusted per 1 hour increase in ONF period: β=-0.02, 95% CI, -0.05–0.00, p=0.054) and in % body weight change (β=-0.03, 95% CI, -0.06-0.00, p=0.035). In stratified analyses, associations were statistically significant only in women, and among individuals ≤60 y. Results were not modified by ONF midpoint (i.e., earlier vs. later eating distribution), or by BMI in 2015.

Conclusions: Longer ONF was associated with a slight but statistically significant weight loss over six years that was more robust in women and younger adults. The magnitude of weight change, though in the hypothesized direction, suggests that ONF may better serve as a potential weight maintenance than weight loss strategy.

Funding Sources: The American Cancer Society funds the creation, maintenance, and updating of the Cancer Prevention Study-3 cohort.