Impact of Meal Timing on Polycystic Ovary Syndrome Risk during Adolescence

Introduction: Polycystic Ovary Syndrome (PCOS) is a prevalent endocrine disorder that can develop during the post-menarcheal years in adolescence. Timing of dietary intake, such as night-time eating, has been associated with obesity and insulin resistance, which are known to both exacerbate and underlie emergence of PCOS in adolescence. The objective of this study was to determine whether the distribution of caloric intake throughout the day within the first post-menarcheal year is associated with PCOS or individual PCOS symptoms 6-12 months later. We hypothesized that caloric density over the course of the day, overall and by macronutrient, would differ in those who would go on to meet criteria for PCOS. Methods: An ancillary study of dietary intake was conducted alongside a prospective cohort study of adolescents (n=31) followed from 6-10 months post-menarche to 2 years post-menarche. Study visits occurred at the following gynecological time points: 6-10 months, ~1-, ~1.5-, and ~2 years post-menarche and included fasting venipuncture to measure reproductive and metabolic hormones, anthropometry, and two 24-hour diet recalls to estimate usual dietary intake. The relative percent caloric intake, total and by macronutrient, in the morning (0400-1159), daytime (1200-2159), and nighttime (2200-0359) was computed for weekdays and weekends across the first two study visits, representing the first post-menarcheal year. PCOS was evaluated at 1.5 (n=4) and 2 years post-menarche (n=27). Mann-Whitney U-Tests compared dietary intake based on final phenotype and Spearman’s Rank Correlation Coefficients were used to evaluate the association between diet variables, symptoms of PCOS, and metabolic dysfunction. Results: The distribution of total kilocalories (kcal) and macronutrient intake on weekend days, but not weekdays, during the first post-menarcheal year differed between adolescent girls who later met criteria for PCOS (n=7) versus regular cycles (n=9). Adolescents who ultimately met criteria for PCOS consumed a greater portion of their total kilocalories (kcal) in the morning versus adolescents with regular cycles (31 [22.0-39.4] % vs 15 [9.2-28.7] %, p=0.03), which was driven by a higher relative intake of carbohydrates (22% vs 18%, p=0.07). Observed differences in dietary composition over the day may be related to meal skipping; within the first year of menarche, adolescents who developed PCOS tended to be less likely to skip meals (0% vs 25%, p=0.08). Higher relative intake added sugar in the morning was associated with lower luteinizing hormone (LH; rho=-0.457, p=0.01; n=31), whereas consuming a greater proportion of added sugars in the afternoon tended to be associated with higher LH (rho=0.450, p=0.01; n=31). Conclusions: While preliminary, differences in eating patterns across the day during early post-menarcheal years may be associated with an increased risk of PCOS. Additional research is underway to expand these findings into more diverse populations and with larger sample sizes. NIH R21 (PI: M Lujan, Cornell University), CIHR Fellowship (PI: H Vanden Brink), Texas A&M AgriLife. Research sites: Children’s Mercy Kansas City and Cornell University. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.