A sniff of dark chocolate before leg extensions may do more than make the gym smell better.
A Frontiers in Physiology study found smelling chocolate before and between sets of resistance exercise increased training volume in moderately trained men, with dark chocolate linked to lower hunger and 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 senior author Dr Mohamed Nashrudin bin Naharudin, an assistant professor at the Faculty of Sports and Exercise Science at the University of Malaya.
“Seeing a substantial increase in repetitions without the athletes feeling like they were exerting themselves any harder is a fascinating psychobiological outcome.”
The study involved 23 healthy, moderately trained men in their early to mid-20s. They were divided into three groups and given one of three odor samples: liquified dark chocolate containing 90 percent cocoa, liquified milk chocolate containing 60 percent cocoa, or water as a control.
“We know olfaction is powerfully wired into the brain’s appetite and emotion networks, but surprisingly, no study has systematically looked at the three-way interaction between smell, appetite, and actual resistance exercise capacity,” said Nashrudin Naharudin.
Participants had not eaten for at least 10 hours before performing leg extensions. Researchers assessed leg extension performance before and during training.
Before the workout, participants reported hunger, fullness, desire to eat, and plans to eat in the near future. During the sets, researchers measured only hunger and desire to eat, after 30 seconds of exposure to a scent sample.
The results showed the two chocolate odors had different effects.
Compared with the water control and milk chocolate samples, smelling dark chocolate consistently led participants to report less hunger, less desire and intention to eat, and greater fullness before exercise. The researchers said this smell mainly suppressed appetite by reducing hunger and increasing fullness.
Participants who smelled the milk chocolate sample reported higher odor pleasantness than those exposed to dark chocolate and water, but no changes in hunger or appetite.
The chocolate odors also affected performance.
“Sniffing a 90 percent dark chocolate odor added about 18 more repetitions to participants’ leg extensions, while a 60 percent milk chocolate odor added about nine repetitions compared to the water control,” said Nashrudin Naharudin.
The researchers said these shifts in appetite perception may be tied to learned cues linked to foods people have eaten before.
“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,” said Nashrudin Naharudin.
“Conversely, the sweeter milk chocolate scent acts more like a hedonic reward cue, enhancing training volume by creating a highly pleasant sensory environment rather than by shifting basic metabolic hunger signals.”
The authors said their claims remain inferential because no blood hormones or neural pathways were measured. They also noted there may have been slight variations in smell intensity between the chocolate samples, and the water sample was odorless, which could have signalled to participants that they were in the control group.
They said more diverse participant samples are also needed to confirm the findings.
“We don’t think chocolate is entirely unique, though it is a food cue with incredibly strong, universally recognized reward associations,” Nashrudin Naharudin concluded.
“A person likely needs to find the odor familiar and appealing – or at least not repulsive – to trigger the psychological shift in appetite that’s needed to see a performance boost.”
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