Smelling chocolate before a workout sounds like the setup for a wellness hack. A small new study suggests the reality is more interesting, and much less practical, than that.
The exploratory study, published in Frontiers in Physiology, found that young men who smelled dark or milk chocolate before and during a fasted leg-extension workout completed more repetitions than those exposed to an odorless water control. The study also found that dark chocolate odor appeared to reduce hunger ratings before exercise. But the research involved only 23 healthy, moderately trained men, measured one exercise task in a lab and did not test whether smelling chocolate improves real-world workouts, long-term fitness or eating behavior.
The study looked at a question that is easy to overlook: Can food smells affect appetite and physical effort even when no food is eaten?
Researchers divided participants into three groups. Each group was exposed to one sample: liquified dark chocolate with 90% cocoa, liquified milk chocolate with 60% cocoa or water. Participants had fasted for at least 10 hours before performing leg extensions, a resistance exercise that involves lifting weight by extending the lower legs while seated.
Before exercise, participants reported hunger, fullness, desire to eat and whether they planned to eat soon. During the workout, researchers measured hunger and desire to eat after brief exposure to the assigned scent.
The two chocolate odors appeared to affect participants differently. Compared with the water control and milk chocolate samples, dark chocolate odor was linked with lower hunger, lower desire and intention to eat and greater fullness before exercise. Milk chocolate odor was rated as more pleasant than dark chocolate or water, but it was not linked with the same changes in hunger or fullness.
The chocolate odors were also linked with higher training volume. Participants exposed to dark chocolate odor completed about 18 more leg-extension repetitions than the control group, while those exposed to milk chocolate odor completed about nine more repetitions.
“Exposing moderately trained men to chocolate odors right before and between sets of resistance exercise significantly increased their overall training volume without increasing their perceived exertion,” said Dr. Mohamed Nashrudin bin Naharudin, senior author of the study and an assistant professor at the Faculty of Sports and Exercise Science at the University of Malaya.
That does not mean chocolate scent is a proven performance tool. The study was small, short-term and tightly controlled. It did not include women, older adults, beginners or people with different fitness levels. It also did not measure hormones, brain activity or digestive responses that could explain why the odors appeared to change hunger or exercise performance.
The control condition also matters. Water has no odor, so participants may have been able to tell whether they were in the chocolate or control group. That makes it harder to separate the effect of the scent itself from expectation, novelty or the pleasantness of smelling chocolate in a lab.
The researchers suggested that food odors may act as learned cues. A dark chocolate smell could signal a rich, filling food, while milk chocolate may create a more pleasant sensory environment. Either way, the findings point less to chocolate itself and more to how smell, expectation, hunger and effort may be connected.
“The dark chocolate scent serves as a learned cue for a rich, bitter, and highly satiating food, which essentially tricks the system into an anticipatory state of fullness,” Nashrudin Naharudin said.
That idea is plausible, but still early. The study did not show that smelling chocolate changes what people eat later, reduces calorie intake or makes fasted exercise better. It also does not mean people should skip food before training or use food smells to suppress hunger.
What it does show is that food cues can have measurable effects, at least in a small lab setting. Smell is closely tied to appetite, memory and emotion, so it makes sense that a familiar food odor might shift how hungry, full or motivated someone feels in the moment.
The authors reported that they did not receive financial support for the study or its publication.