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One small 2026 study found that 23 moderately trained men completed more leg-extension repetitions after smelling prepared dark- or milk-chocolate odors than after a water-based control. It did not establish whether the difference was mostly psychological: appetite and pleasantness ratings changed, but the study could not show that those changes caused the performance result or separate them from expectation. The finding applies to one fasted laboratory exercise test, not workouts or athletes generally.
What the study found
Fan and colleagues reported the randomized, double-blind, crossover study in Frontiers in Physiology on July 9, 2026. The 23 participants were moderately trained men. After an overnight fast, each completed repeated sets of leg extensions at 80% of his individual 10-repetition maximum, continuing each set to volitional exhaustion. The researchers compared three conditions: prepared 90% dark-chocolate odor, prepared 60% milk-chocolate odor, and a water-based control. Participants were exposed to the assigned odor repeatedly before sets.
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Total repetitions were higher with both chocolate odors than with the control in this protocol. The dark-chocolate condition was associated with 18 more total repetitions than control (95% confidence interval 13.8 to 22.1; p < 0.01); the milk-chocolate condition was associated with 9 more (p < 0.01). These are differences in total repetitions across the study’s leg-extension sets, not percentage gains or estimates for a whole workout. The registry lists total leg-extension repetitions as the primary outcome.
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How the two odors differed in the reported findings
| Condition | Repetitions versus water control | Reported subjective finding |
|---|---|---|
| Prepared 90% dark-chocolate odor | 18 more total repetitions; 95% CI 13.8 to 22.1; p < 0.01 | Reduced appetite-related ratings before exercise |
| Prepared 60% milk-chocolate odor | 9 more total repetitions; p < 0.01 | Increased odor pleasantness |
| Water-based control | Reference condition | Odorless and highly identifiable to participants, according to the authors |
The table reflects one small study and does not show that dark chocolate is a better workout aid than milk chocolate. The two odor conditions had different reported repetition differences and subjective profiles, but the findings are not a direct demonstration that one aroma is more effective than the other. Both were compared with the same control under the same narrow protocol.
How to read the repetition numbers
The reported differences are totals for the study’s leg-extension work, rather than 18 or 9 extra repetitions in every set. They are comparisons against the water-control condition in this particular experiment. The dark-chocolate estimate also came with a confidence interval: the study’s estimate was 18 additional repetitions, with the interval reported as 13.8 to 22.1. The milk-chocolate result was reported as 9 more repetitions, but the summary does not provide a confidence interval for that comparison.
Both comparisons were reported with p < 0.01. That statistic does not mean there is a 99% chance that chocolate odor will improve an individual’s workout. It describes the results under the statistical test and study conditions; it does not resolve whether the finding will replicate, how large an effect would be in another activity, or why the difference occurred. Likewise, a difference in total repetitions during one laboratory session is not evidence of greater strength, muscle growth, or better fitness over time.
The randomized crossover format lets researchers compare conditions within a study designed around participants experiencing the different conditions, rather than treating the three groups as entirely separate populations. It does not remove every source of bias. In particular, a highly recognizable odorless control can still make the conditions feel different to participants, even when the study is described as double blind.
Was the effect mostly psychological?
The study cannot answer that. “Psychological” can refer to several overlapping possibilities: a person’s expectation about an odor, how pleasant it seems, changes in appetite or attention, or the way sensations influence effort. A performance response could involve subjective experience without being merely imaginary. But this trial did not measure enough to determine which pathway, if any, produced the repetition differences.
Before exercise, dark-chocolate odor reduced appetite-related ratings, while milk-chocolate odor increased pleasantness ratings. Lower hunger and greater fullness were associated with better performance. Those associations are not proof that feeling less hungry or more full caused participants to complete more repetitions. The authors’ exploratory mediation analyses did not establish hunger, fullness, or pleasantness as explanatory mechanisms for the performance differences.
The researchers discuss possible appetite, affective, expectancy, and cephalic-phase pathways. These are proposed explanations, not mechanisms demonstrated by this experiment. The study did not measure appetite hormones, autonomic activity, or neural responses. It therefore cannot tell whether the odor changed a physiological signal, altered a participant’s feelings or expectations, or influenced performance through some combination of factors.
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The study was described as double blind, but the authors caution that the odorless water control was highly identifiable. Participants may have recognized when they were in the control condition and guessed that it was not the active odor. If so, expectations about the chocolate odors—or disappointment with the control—could have affected effort. This possibility does not prove that expectation explains the result; it means the design could not cleanly rule it out.
A stronger test of whether expectation accounts for the difference would need comparison conditions that are harder to distinguish and measurements designed to assess participants’ expectations alongside performance. The authors call for better expectancy-matched controls and objective measurements. Until such work is available, “mostly psychological” is an open question, not the study’s conclusion.
What participants actually smelled
This was not a test of eating chocolate, smelling a chocolate bar, or using a retail product as a pre-workout supplement. Researchers prepared approximately 40 mL liquid stimuli in jars. The dark-chocolate preparation used commercial 90% cocoa chocolate, water, and propylene glycol; the milk-chocolate preparation combined dark chocolate, whole milk, water, and propylene glycol. Participants held a jar about 2–3 cm from their nostrils for 30 seconds, with exposures repeated before exercise sets.
The controlled jar exposure matters when interpreting the result. The study did not establish that an ordinary chocolate aroma, a different preparation, a shorter exposure, or a product used at home would have the same effect. Nor did it test whether eating chocolate improves exercise performance. Smell exposure and food consumption are different interventions, and the results for one should not be assigned to the other.
The use of a prepared stimulus also means there is no tested consumer dose or practical recipe to copy. The study’s approximately 40 mL describes the liquid prepared in a jar; it is not a dose of chocolate to eat, a measured amount of aroma in the air, or a recommendation for a workout routine. The reported protocol gives the jar distance and exposure duration, but the study does not establish that retail chocolate or a home-made version will deliver the same odor exposure.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How far the result can be generalized
The evidence is specific to 23 young, moderately trained men performing a single-joint leg-extension task after an overnight fast. It does not show that smelling chocolate improves running, cycling, team sports, a full-body gym session, or everyday exercise. It also does not establish an effect for women, older adults, beginners, elite athletes, or other groups not represented by this sample.
Nutrition is another important boundary. Because participants exercised after an overnight fast, the study cannot show whether the same result would occur after a meal or snack. The appetite findings may be particularly relevant to the study’s fasting context, but they do not tell us how odor exposure affects people in other nutritional states.
Finally, the number of repetitions in this controlled test is not a measure of long-term strength, muscle growth, fitness, or health. The researchers assessed performance in a particular exercise session; the study does not show whether any acute difference persists, repeats across sessions, or leads to a training benefit.
What future studies would need to test
The authors call for replication across exercise types, nutritional states, and more diverse populations. A useful follow-up would also need controls that participants cannot easily distinguish from the chocolate odors, while measuring expectations and relevant objective responses. Those design improvements would address the central uncertainties here: whether the repetition difference recurs, whether it depends on being fasted or on doing leg extensions, and whether expectation, appetite, pleasantness, or another pathway helps explain it.
Until those questions are answered, there is no evidence-based reason to buy a particular chocolate bar, eat chocolate, or add a special smelling routine to training on the strength of this result. A 90% cocoa chocolate bar is only an adjacent product example because commercial 90% cocoa chocolate was used to prepare one laboratory odor stimulus. The study did not test a retail bar as a workout aid or establish a product recommendation.
What a reader can reasonably take from it
- There is a preliminary signal: in this experiment, fasted, moderately trained men completed more leg-extension repetitions after prepared chocolate-odor exposure than after the water control.
- The mechanism is unresolved: appetite and pleasantness ratings changed, but mediation analyses did not establish that either explained the repetition differences.
- Expectation remains a possible contributor: the odorless control was recognizable, so the study could not rule out an effect of participants’ expectations.
- The result is not a general exercise recommendation: the trial does not demonstrate a benefit across activities, populations, or post-meal exercise.
- It is not evidence for eating chocolate before exercise: the tested intervention was a prepared odor exposure, not chocolate consumption.
For now, smelling chocolate can be described as an experimental condition associated with more repetitions in one small laboratory study—not as a proven way to improve a workout. Replication in larger and more diverse groups, across exercise types and nutritional states, with controls that better match participants’ expectations, would be needed to clarify whether the finding is reliable and what accounts for it.
Frequently Asked Questions
Can smelling chocolate make a workout easier?
The study found more leg-extension repetitions after chocolate-odor exposure, but perceived exertion did not clearly differ between odor conditions. It therefore did not show that the exercise felt easier, and it tested only one fasted laboratory protocol.
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Was dark chocolate better than milk chocolate for exercise?
Dark-chocolate odor was associated with 18 more total repetitions than water control, while milk-chocolate odor was associated with 9 more. The study did not establish that dark odor was directly superior to milk odor or that either is a proven workout aid.
Did the study test eating chocolate before exercise?
No. Participants smelled prepared liquid odor samples in jars. The trial does not show that eating chocolate, smelling a retail chocolate bar, or using a chocolate product improves performance.
Does chocolate smell improve running or other kinds of exercise?
That remains unknown. The study involved 23 moderately trained men doing repeated leg-extension sets after an overnight fast; it did not test running, cycling, sports, or a full workout.
Was the result psychological?
The trial cannot determine that. Appetite and pleasantness ratings changed, but exploratory mediation analyses did not establish them as explanations, and the recognizable water control may have allowed expectations to influence effort.
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The Bottom Line
One exploratory study found more leg-extension repetitions after prepared chocolate odors, but it cannot show that smelling chocolate generally improves exercise or whether expectation, appetite, or another pathway explains the result. It is not evidence for eating chocolate as a performance supplement.
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