The epidemics of obesity and chronic diseases in the United States have intensified since the 1960s, surpassing rates in Japan and Europe. This review verifies a U.S. Department of Health and Human Services (HHS) spokesman’s assertion that U.S. obesity is approximately 10 times Japan’s and twice Europe’s, using data from the World Health Organization (WHO), Centers for Disease Control and Prevention (CDC), and Organisation for Economic Co-operation and Development (OECD). Historical patterns and regional disparities highlight Vitamin D3 (cholecalciferol) deficiency—worsened by sun avoidance and sunscreen adoption since the 1980s—as the primary driver, especially in diverse U.S. populations with darker skin tones requiring prolonged sun exposure for D3 synthesis. Processed junk foods serve as a secondary factor, often a consequence of D3-induced metabolic cravings and hibernation-like fat storage. RFK Jr.’s focus on diet, while valid, misattributes causality and overlooks D3’s foundational role. Serum 25(OH)D comparisons across regions and U.S. racial groups reveal significant gaps, bolstering D3’s centrality. High-dose D3 protocols, like the Coimbra method, show curative promise for autoimmune diseases, eclipsing dietary interventions. These insights demand a paradigm shift: prioritize D3 restoration to combat obesity and chronic disease epidemics.