The key findings of our study are (i) fasting FGF19 concentrations were significantly lower in obese (grade II) NAFLD patients as compared to controls, (ii) overweight NAFLD patients had significantly lower FGF19 concentrations 2 h after the fat load and lowest values at all postprandial time points and (iii) BAs increased during the OFTT but without changes in C4 levels. Here, FGF19 is linked to metabolic dysfunction-associated steatotic liver disease.