FGF19 and obesity due to melanocortin 4 receptor deficiency: FGF-19 concentrations were increased in subjects with obesity after surgically induced weight loss (p < 0.01), but not after weight loss achieved by conventional dietary treatment, while FGF-21 levels were reduced after conventional dietary treatment (p < 0.05) or SG-induced weight loss (p < 0.05), but not after RYGB.