Mechanistic studies demonstrate that 25-hydroxyvitamin D (25(OH)D) modulates obesity through distinct pathways: First, it binds to the vitamin D receptor (VDR) to upregulate lipolytic genes while suppressing adipogenic gene expression, thereby inhibiting adipocyte differentiation and lipid accumulation (22); second, it rapidly elevates intracellular calcium levels to activate calcium-mediated signaling cascades, triggering apoptosis in mature adipocytes (23). The gene discussed is VDR; the disease is obesity disorder.