The Mass Balance Model (MBM) proposes that human body weight regulation is more accurately described by direct mass accounting than by indirect energy balance. This article establishes the MBM Reference Framework, a living document that consolidates, corrects, and extends the prior MBM series. It presents the complete open-system mass balance equation, which explicitly includes inhaled molecular oxygen and insensible evaporative water losses. It states the open-system formulation of the First Law of Thermodynamics and clarifies why an energy balance equation – even when correctly formulated – does not uniquely determine mass change. It presents the corrected stoichiometric equations for substrate oxidation and qualifies the nitrogen-to-protein conversion factor as an empirical average rather than an exact atomic constant. It distinguishes the MBM from both the static CICO heuristic and from multi-compartment dynamic Energy Balance Models, acknowledging the methodological sophistication of the latter while arguing that they remain anchored in the two-step mass-to-energy conversion. It calibrates translational applications to realistic physiological timeframes and states the limitations of the current evidence base. Finally, it documents, in a dedicated section, every technical correction relative to earlier MBM preprints. The framework is offered as a living reference for the MBM research program and will be updated as new evidence becomes available.