In this study, the authors examined the reward value of sweeteners in mice by assessing the animals' preferences for sweeteners compared to lick-induced optogenetic activation of midbrain dopaminergic neurons. They found that mice preferred optogenetic stimulation to the artificial sweetener sucralose, but not to sucrose. Interestingly, following a period of food restriction, the reward value of sucrose increased, whereas after administration of leptin it decreased. These results highlight the post-ingestive effects of fat metabolism on nutrient preference.