Black rice (BR) is considered one of the healthiest foods worldwide. This study assessed the bioactive compound contents and antioxidant activities of the distilled water (DW) and 80% ethanol (EtOH) extracts of BR, black rice bran (BRB), and milled black rice (MBR). In addition, their anti-obesity, anti-obesogenic, and anti-muscle atrophy effects were comparatively evaluated. The results revealed that the 80% EtOH extract of BR contained higher contents of β-glucan, total flavonoids, and total phenolics (26.97 ± 0.70 mg gallic acid equivalents (GAE)/g and 16.58 ± 0.37 mg quercetin equivalents (QE)/g, respectively) and showed higher antioxidant activity than those of the BRB and MBR extracts. On the other hand, BRB contained the highest content of γ-oryzanol, which was 15.12 ± 0.03 mg/g. Moreover, the 80% EtOH extract of BR exhibited a stronger anti-obesogenic effect by downregulating adipogenesis-related proteins (PPAR-γ, C/EBP-α, and FAS) and upregulating lipolysis-related proteins (PGC-1α and CPT-1), while the BRB extract effectively increased myotube diameter and fusion index. Overall, these findings indicate that the 80% EtOH extracts of BR, BRB, and MBR, particularly the BR extract, have high potential as natural antioxidants and anti-obesity agents, with BRB showing promise in preventing muscle atrophy.