Discussion
obesity, weight loss
OBESITY
In this randomized, single-center, double-blind, placebo-controlled, parallel group, prospective clinical trial, we investigated whether GLP-1 analog liraglutide affects food-related liking in participants with OB using an fMRI-compatible gustometer. We measured both self-reports of liking and neural responses.Behaviorally, and contrary to our hypothesis, we did not find any statistical evidence that our intervention impacted food liking. We must always be careful when interpreting the absence of significant main effects or of a significant interaction effect. As in any experiment, we cannot exclude classical limitations such as methodological aspects or sample size. For instance, our sensitivity analysis showed that we could detect a small to medium effect of the intervention on liking perception, therefore we cannot exclude the presence of a small effect. However, our Bayesian approach provides strong evidence favoring the null hypothesis, which suggests that self-reported liking did not differ between the liraglutide and placebo groups or between pre- and post-intervention ratings.As for the brain activity, analyses of the participants’ neural responses to the milkshake and control taste stimulus revealed a main effect of the liking modulator activating the vmPFC and the amygdala; these brain regions are known to be involved in reward processing [Taken together, our results do not provide evidence that liraglutide alters liking while consuming food. This contrasts with recent findings showing that weight loss was associated with a decrease in food liking [While we did not find evidence suggesting that liraglutide changed the milkshake liking, we did find evidence indicating that the milkshake was less pleasant in the second session compared to the first for both groups. This effect was therefore independent of the GLP-1 analog treatment. It is unclear which factor(s) this effect is driven by given the absence of a control group without a weight loss intervention in our current study. It could be driven by the weight loss intervention, but differences in BMI did not significantly correlate with liking of the milkshake in a previous study using similar stimuli [Another well documented effect we found is a large effect of the medication on weight loss. As expected and previously documented [However, the weight loss induced by liraglutide was not our main research question—the present study focused on the liking component of reward. While there are a few studies on the wanting component (e.g., [To conclude, this study suggests that liraglutide leads to weight loss but does not provide evidence that it is due to a change in food-related liking in participants with obesity.