Each hour delay in starting daily food intake was associated with 0.88 mU/l higher fasting insulin, 16.17 mU/l higher post-meal insulin, and 0.30 units higher insulin resistance (HOMA-IR) among 297 prediabetic adults. Later eating start also correlated with 0.81% higher body fat per delayed hour, independent of total calories or food composition. The circadian timing of first food intake appears more metabolically consequential than previously recognized. This finding challenges conventional diabetes prevention approaches that emphasize only caloric restriction and macronutrient balance. The meal timing-insulin relationship persisted even after adjusting for body composition, suggesting direct chronobiological effects on glucose metabolism rather than indirect weight-mediated pathways. For the 88 million Americans with prediabetes, shifting breakfast earlier could represent a simple intervention to improve insulin sensitivity and potentially delay type 2 diabetes progression. However, this preprint awaits peer review, and the observational design cannot establish causation. The relatively homogeneous European cohort may limit generalizability across populations with different cultural eating patterns and genetic backgrounds.