Abstract
INTRODUCTION: Given insulin resistance's (IR) critical role in metabolic pathophysiology, this study aims to identify optimal coffee consumption patterns by timing and dose to improve population health. MATERIAL AND METHODS: Multivariate logistic regression and restricted cubic splines assessed associations between coffee timing, dosage, and IR (measured by estimated glucose disposal rate) from NHANES data (1999-2018). Interaction and subgroup analyses explored variations across population segments. RESULTS: We analysed 21,138 participants, of whom 46.79% were non-consumers. Among consumers, 76% primarily drank coffee in the morning. Morning consumption at the lowest quartile (Q1) showed significant improvement in IR (odds ratio [OR] = 1.37, 95% confidence interval [CI]: 1.16-1.62), although this benefit diminished with higher consumption levels (p < 0.05). While the "all-day" pattern overall showed a non-significant trend toward improved insulin resistance (OR = 1.20, 95% CI: 0.83-1.73), higher consumption within this pattern (Q3: OR = 1.46, 95% CI: 1.13-1.89; Q4: OR = 1.34, 95% CI: 1.11-1.63) proved significantly more beneficial than lower intake. Comparative analysis revealed that morning consumption tended to be more advantageous for low-to-moderate intake (Q1-Q2), whereas all-day distribution showed potential benefits at higher consumption levels (Q3-Q4). The observed benefits were primarily associated with caffeinated coffee, attenuated by sugar addition, and varied across subgroups based on age, sex, and comorbidities. CONCLUSIONS: Both morning and all-day coffee intake improve IR. For moderate consumption (1-2 cups/day), morning intake provides optimal improvement in insulin sensitivity. For higher intake (≥ 3 cups/day), distributed consumption is more effective. These findings support chrono-nutrition principles for optimising metabolic health through coffee consumption.