BDNF and depressive symptom measurement: Two RCTs—one conducted in obese women with mild to moderate depressive symptoms [40] and the other conducted in adults with obesity and mild depression [39]—have already shown that ≥2000 IU cholecalciferol daily for 8–12 weeks increases serum BDNF levels (≈ +7%) and reduces BDI-II by 2–8 points.