Transgenic overexpression of FGF19 in mouse skeletal muscle results in the accumulation of FGF19 in serum, and reverses high fat diet (HFD)-induced weight gain and various metabolic defects associated with obesity, including hepatic lipid accumulation, insulin resistance, and increased serum lipid levels [3], [4]. This evidence concerns the gene FGF19 and obesity due to melanocortin 4 receptor deficiency.