Collectively, our behavioural and fMRI findings reveal that GLP-1 receptor activation normalizes associative learning in insulin-resistant humans by modulating the encoding of adaptive prediction errors within the mesoaccumbens pathway, indicating that DA-driven learning processes depend on metabolic signalling, and this may contribute to the weight-reducing effects of liraglutide in obesity. Here, GLP1R is linked to obesity due to melanocortin 4 receptor deficiency.