Daily administration of B-3, a probiotic strain for anti-obesity, promoted mitochondrial biogenesis through the AMPK-PGC-1α signaling pathway in skeletal muscle, and the distribution of oxidative muscle fibers through increasing in PGC-1α gene expression; and induced muscle hypertrophy through the Akt signaling pathway in rats. The gene discussed is PPARGC1A; the disease is obesity due to melanocortin 4 receptor deficiency.