Dark chocolate scent may boost exercise performance

Clinical takeaway: For patients training in a fasted state, brief exposures to a dark chocolate odor may support more work per session. But the evidence is only from a small, proof-of-concept trial.

Plenty of patients train on an empty stomach. Tight morning schedules and intermittent fasting can push workouts into a fasted window. But one risk with this strategy is that hunger can cut those sessions short. A new crossover trial tested an unusual workaround: smell. Resistance-training men completed more reps when a dark chocolate odor was presented before and between sets.

Compared with an odorless water control, a dark chocolate odor added about 18 leg-extension reps. A milk chocolate odor added about nine reps. Perceived exertion increased as the sets wore on, as expected, but did not differ with the introduction of either odor.

Dark chocolate blunted appetite: men reported less hunger, less desire to eat, and more fullness while fasting. Since lower hunger has tracked with better lifting in earlier work, appetite looked like the likely driver. Milk chocolate did not affect appetite, but was rated as more pleasant to smell.

Yet when the researchers tested whether appetite or pleasantness explained the extra reps, neither held up. One untested possibility is a cephalic-phase response, the body reacting to a food smell as if a meal were coming, but no hormones or autonomic signals were measured. The performance gain was real, but why it happened was unconfirmed.

The trial was a randomized, double-blind crossover in 23 resistance-trained men in their early 20s. Each man completed all three odor conditions on separate days, fasted at least 10 hours, doing leg extensions to exhaustion while a dark chocolate, milk chocolate, or water odor was presented before and between sets.

Because no hormones or autonomic signals were measured, those potential mechanisms need direct biological confirmation. A placebo with a scent would separate out the impact of a smell itself. The effect needs testing in broader populations across a wider range of exercises.

"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," suggested Mohamed Nashrudin bin Naharudin, an assistant professor at the Faculty of Sports and Exercise Science at the University of Malaya and the study's senior author.

Source: Fan X, et al. (2026 Jul 9) Front Physiol. Chocolate odor enhances resistance exercise performance through appetite suppression in the fasted state: an exploratory study