GIP and obesity due to melanocortin 4 receptor deficiency: Mice in which GIP-action is prevented by knocking out the GIP-receptor (Miyawaki et al., 2002), by treatment with a GIP-receptor antagonist (Gault et al., 2005, 2007) or by ablation of GIP-secreting cells (Althage et al., 2008), are somewhat protected from developing obesity on a high-fat diet or on the leptin-deficient, hence overeating, ob/ob-background.