Modulating hunger and food craving through expectations: placebo and nocebo effects of sham vagus nerve stimulation on food-related experiences.

Placebo and nocebo effects—beneficial or adverse outcomes driven by expectations rather than active treatment components—are well documented in domains such as pain, mental health disorders, fatigue etc. However, their influence on food metabolism and food-related behaviors remains underexplored. This study investigated whether verbal suggestions about the effects of a sham vagus nerve stimulation could alter hunger, food craving, food desirability, and food choice in healthy volunteers. In a randomized, single-blind, between-subjects design, 126 participants were allocated to a placebo, nocebo, or control group. Participants in the placebo group were told the stimulation would reduce hunger, while those in the nocebo group were told it would increase hunger; the control group received neutral information. Self-reported hunger and craving were measured at four time points throughout the session, along with food desirability ratings and food choices between natural and ultra-processed options.Results showed that verbal suggestions effectively altered participants' expectations, which in turn influenced food craving and hunger ratings. Specifically, the placebo group reported reduced overall craving in comparison to the control group and less hunger in comparison to the nocebo group after the food-related tasks. The nocebo group showed an increase in hunger and no increase in subjective overall craving. Additionally, no effects of suggestions on food desirability and choice were found.These findings provide novel evidence that expectations shaped by verbal suggestion can influence food-related experiences with potential implications for interventions targeting eating habits and obesity prevention.