The Supersaturated Hydrogen-Rich Water for Outpatients with Persistent Excess Weight (HOPE) study is a Phase III, multicenter, randomized, double-blind, placebo-controlled study designed to evaluate the efficacy and safety of daily consumption of supersaturated hydrogen-rich water in adults with persistent excess body weight. The trial investigates whether sustained exposure to molecular hydrogen can favorably influence body composition and key metabolic outcomes compared with a placebo water lacking dissolved hydrogen. By enrolling outpatients across multiple centers and applying rigorous blinding and randomization procedures, HOPE aims to generate high-quality clinical evidence on the potential role of hydrogen-rich water as a non-pharmacological, adjunctive strategy for weight management and metabolic health.