Body-Corrected Ketogenic Ratio: A Subject-Centered Boundary Model for Integrating Endogenous Fat Availability into Ketogenic Nutrition

The ketogenic ratio has traditionally been treated as a property of the diet: a relationship between ketogenic and anti-ketogenic macronutrient components. This diet-centered framing is useful in classical therapeutic ketogenic protocols, but it may be incomplete in weight-loss, body-composition, and recomposition contexts, where endogenous fat can contribute to whole-body ketogenic substrate availability. This manuscript introduces a subject-centered reformulation: the ketogenic ratio should be interpreted not only as a property of food, but also as a property of the subject. BKR is defined as a body-composition proxy for endogenous ketogenic reserve: the relationship between total fat mass, used as an adipose-reserve proxy, and estimated structural protein-equivalent mass (SPEM). Corrective prescription is framed as a boundary condition rather than a calculated dose: when the dietary fat-to-protein-equivalent ratio is maintained below the subject's own current BKR under sufficiently low-carbohydrate conditions, the model predicts corrective pressure toward endogenous fat mobilization. Population-derived BKR targets are reference landmarks, not prescriptive thresholds. The manuscript presents provisional equations, individual-level National Health and Nutrition Examination Survey (NHANES) 2015-2018 dual-energy X-ray absorptiometry (DXA) calibration, alpha sensitivity analysis, worked examples, ecological comparison, mechanistic rationale, and falsifiable predictions. At alpha = 0.25, mean BKR was 1.59 in adult men and 2.71 in adult women aged 20-59 years; among normal-BMI adults, median BKR was 1.14 in men and 2.08 in women. Lower-adiposity strata support provisional lean reference landmarks around 0.75-0.95 for men and 1.30-1.55 for women. This model is not yet a validated clinical prescription tool and is presented as a theoretical framework with empirical body-composition calibration.