The smell of chocolate can make us want to eat it. But could spending time with that aroma also be satisfying in itself? Research findings differ on whether food odors increase appetite or reduce desire for a particular food.
Rachel Hagan and colleagues investigated this question through behavior: how much effort people exert to obtain a food they want. After five minutes in a room scented with chocolate or orange, they found no evidence that motivation to obtain the corresponding food increased or decreased. In a separate experiment involving actual eating, however, responses to the consumed food changed.
Separating liking from wanting
As we continue eating a food, its appeal may decline while another food still seems attractive. This decline in liking for an eaten food relative to foods not eaten is called sensory-specific satiety. The term does not simply mean a full stomach; it describes a change in response to a particular food.
Some studies report similar changes from smell alone, while others suggest that food odors increase desire. This study therefore focused on motivation to obtain food as a reward rather than judgments of how good it tastes when eaten.
The main aim was to test whether an ambient food odor strengthens or weakens food-seeking behavior. A separate group of participants was also tested to see whether the same task could detect changes after actual consumption. The choice of a food to take home provided an additional measure.
Spending time in a scented room versus actually eating
The odor experiment recruited 38 people and the eating experiment 40. After exclusions, the analyses included 37 and 38 participants, respectively. These were separate groups recruited at different times, not the same people taking part in both experiments.
Within each experiment, participants were alternately assigned to the chocolate or orange condition. They were asked to abstain from food and drink other than water for at least three hours before attending.
In the odor experiment, participants spent five minutes in a room where chocolate or orange fragrance had already been diffused, completing a reading task unrelated to food. They were not told beforehand that the experiment concerned smell, to avoid directing their attention to the room’s odor. Only two reported noticing a smell before being informed about it.
In the eating experiment, participants went to a separate room and ate as much chocolate cake or small citrus fruit as they wanted over five minutes. In both experiments, the same grip-force task was performed before and after the intervention.
Squeezing harder for food that is more wanted
The task briefly displayed images of chocolate cake, oranges, and a teapot used for comparison. Participants were told to squeeze a hand-held dynamometer harder the more they wanted the pictured food. Their maximum grip strength was measured beforehand so that responses could be compared while accounting for differences in strength.
Images appeared for either 33 or 200 milliseconds. Even at the shorter duration, participants later identified approximately 96% of images correctly. The results therefore cannot be described as an experiment in which unseen images acted unconsciously.
Overall force exertion might also decline over the course of testing. The main analysis therefore subtracted responses to the comparison image from responses to food images, focusing on changes specific to food motivation.
At the end, participants chose an orange or a piece of chocolate cake to take home. They chose in a separate room to reduce the influence of being watched by a researcher. This choice occurred approximately 30 minutes after odor exposure, not immediately afterward.
Odor alone produced no detectable food-specific change
In both experiments, participants squeezed harder for food images than for teapot images. This confirmed that the task was responsive to motivation to obtain food.
In the odor experiment, however, the chocolate- and orange-odor groups did not show different pre-to-post changes in force for the corresponding foods. The main measure supported neither the prediction that the odor would increase desire nor the prediction that smell alone would produce satisfaction with that food.
Take-home food choices also did not differ significantly according to the odor experienced. The grip-force and choice measures thus pointed in the same direction.
Actually eating changed responses to chocolate
In the eating experiment, the group that ate chocolate cake showed a significant reduction in force exerted for chocolate images. There was no corresponding decrease for orange images. This selective reduction in desire for the consumed food is consistent with sensory-specific satiety.
In contrast, the citrus-eating group showed no significant pre-to-post change in force for either food image. The effect was not equally apparent for every food consumed.
Take-home choices showed a tendency to select the food not eaten. Among chocolate eaters, 85% chose orange; among citrus eaters, approximately 71% chose chocolate. Motivation measured through grip force and a choice between two foods capture different aspects of behavior.
The amounts eaten were not matched. Mean energy intake was approximately 274 kcal in the chocolate condition and 53 kcal in the citrus condition. The authors suggest differences in energy intake and nutritional composition as possible reasons for the different grip-force results.
Does this mean odors do not affect appetite?
The finding is that this five-minute ambient-odor exposure, assessed with this task, produced no clear enhancement or suppression of food-seeking behavior. The odor experiment had no parallel odorless control group: it compared chocolate odor with orange odor. Further comparisons would be needed to distinguish changes common to both odors from changes due to time or task repetition.
Although compliance with the pre-session food restriction was checked, subjective hunger was not measured during the experiment. Results might differ with odor intensity, exposure duration, the delay before choosing food, or the number of foods offered.
Given discrepancies with previous studies, the authors call for detailed reporting of odor-exposure conditions and replication with larger samples and different timings. Rather than reducing appetite effects to a single simple story, this work asks which behaviors change under which conditions.
Summary
Spending five minutes in a chocolate- or orange-scented room produced no significant odor-condition effects on grip force to obtain related foods or on subsequent food choice. Actual eating, however, reduced effort for chocolate images after chocolate consumption, and choices tended toward the food not eaten.
The study is valuable for testing potential enhancing and suppressing effects of ambient odors with a behavioral task capable of detecting changes after eating. Answering whether smell alone can satisfy desire will require accumulating evidence with clearly specified odor conditions and measures of wanting.
The research was supported by a doctoral studentship funded by BBSRC and GlaxoSmithKline. The authors state that GSK had no role in study design, analysis, or the decision to publish.
References
- Hagan, R., Pawling, R., McGlone, F., & Walker, S. C. (2025; published online in 2024). No evidence for goal priming or sensory specific satiety effects following exposure to ambient food odours. Appetite, 204, 107730. DOI and original article. University repository full text.
