INS and obesity due to melanocortin 4 receptor deficiency: Aside from dopamine, reward-related neural activation alterations in clinically relevant obesity could be associated with peripheral hormone levels (particularly leptin, ghrelin and insulin) which are disturbed in obesity (Leigh & Morris, 2018) and play a role in homeostasis, feeding behavior and reward processing: The ventral striatum might become desensitized to leptin’s inhibitory effect after long-term dietary changes and with increased adiposity (Jastreboff et al., 2014).