Nutramilo Insulin Score (NIS) is a deterministic, source-aware computational surrogate for the Holt Food Insulin Index. Four frozen OLS coefficients (per-1000-kJ density of carbohydrate, protein, fat, fiber) trained on a public n=147 Holt-Bell-Bao cohort, augmented with plant/mixed/animal source multipliers, an energy-normalised pure-fat extrapolation guard, an optional Le-2008 fructose split, and a cross-cohort linear calibration. Primary inferential evaluation is restricted to a strictly out-of-sample n=25 literature-pooled subset. NIS v1.1.9 is positioned as an EXPLORATORY methodology study, not as an externally validated predictive model; a prospective CGM trial is the planned confirmatory step.