GIP and obesity due to melanocortin 4 receptor deficiency: Finally, Matikainen et al. [23] found no change in fasting GLP-1, GIP, and PYY and during an OGTT (GLP-1 and GIP only) before and after a 12-week administration of oral fructose (75 g in 330 mL, 3×/day) in participants with overweight status and obesity.