A recent study has revealed that the scent of chocolate between gym sets prompted men to perform significantly more repetitions compared to when no scent was present. The findings were published in the journal Frontiers in Physiology.
The participants had not eaten for at least ten hours. Yet, a surge of energy emerged, and it was most pronounced after exposure to dark chocolate. They did not perceive themselves as working harder, even as the number of repetitions increased. This gap suggests that the sense of smell affected the brain rather than the muscles, hinting that a simple sensory trick could help people exercise on an empty stomach.
The research team recruited 23 moderately fit men aged 20 to 25. Each arrived at the lab having fasted for at least ten hours. They sat down at a leg extension machine, a staple of strength training, and lifted weights until they could no longer complete another set.
The work was led by Mohamed Nashrudin bin Naharrudin from the University of Malaya (UM) in Kuala Lumpur. He wanted to determine whether the odor alone could influence the amount of weight a person could lift.
Each man came three times, once for each scent. Before and between each session, a researcher held a freshly prepared liquid under his nose. The options were dark chocolate with 90% cocoa content, milk chocolate with 60% cocoa content, or plain water as a neutral control for comparison.
The difference between the scents was substantial. With the smell of dark chocolate, the men completed roughly 18 more leg extensions than with the smell of water, and with milk chocolate, about nine more. The weight remained constant, so their muscles faced the same load each time.
It was this final detail that caught the team’s attention. On a simple scale from zero to ten measuring perceived exertion, the men’s ratings rose as they grew tired, yet the scent under their noses had no effect on these scores.
The increase in repetitions occurred without added strain. “A significant rise in the number of repetitions without a feeling of increased effort is a remarkable psychobiological outcome,” said Naharrudin.
The two types of chocolate acted differently, and this was reflected in the men’s appetite ratings. Before lifting weights, they recorded their hunger, fullness, and desire to eat on a sliding scale.
After exposure to dark chocolate, they reported reduced hunger, greater fullness, and less craving for food. Milk chocolate did not affect hunger signals. It only altered the sensation of pleasure. The men rated its scent as more pleasant than dark chocolate or water, even though it did not dull their appetite.
Naharrudin’s team interprets this gap as a story about expectations. The bitter, sharp scent of dark chocolate signals a filling meal, so the body begins to behave as if a large feast is coming.
“The aroma of dark chocolate acts as a kind of signal for digesting the taste of a rich, bitter, and highly satiating food, which essentially tricks the body and triggers an anticipation of fullness,” Naharrudin said.
Sweeter milk chocolate did not induce a feeling of fullness. Researchers believe it worked more like a reward, making the process more enjoyable and pushing the men to do a few extra repetitions purely for pleasure.
None of this requires food to enter the stomach. Seeing and smelling food can activate the body’s digestive machinery even before the first bite.
Scientists call this the cephalic phase—the head starts eating. This phase describes the activation of saliva production, stomach acid secretion, and hormone release in anticipation of food.
If these signals can shift hunger into fullness, they might also alter the experience of exercise. The men had not eaten, but their bodies seemed to respond as if food was imminent. The anticipation appeared to do some of the work that food normally does.
Researchers have long known that the sense of smell deeply penetrates brain regions responsible for hunger and emotions. A recent study identified a pathway from the nose to the hypothalamus—the brain’s hunger center—which can suppress appetite if a food odor persists. No one had tested whether this wiring could affect how much a person could lift.
Many people exercise before breakfast, whether to fit a workout into a busy morning schedule or as part of a fasting routine. The trade-off is well known. Lifting weights on an empty stomach is often harder, and the workout tends to end sooner. A scent that boosts repetitions without increasing perceived effort could offer a calorie-free way to avoid this.
The result aligns with a strange but real direction in sports science. Athletes who rinse their mouths with a sweet drink and spit it out without swallowing the calories can train harder in some sessions. The effect is most noticeable when they have not eaten.
In one experiment, this mouth-rinse method was found to increase repetitions in difficult exercises without changing the perceived heaviness of the workout. The chocolate scent produced the same effect—greater output without extra strain.
The findings have significant limitations. This was a small study conducted only on men and focused on a single exercise, so it is unclear whether the effect holds for women, older athletes, or a full workout. Hormone levels and brain activity were not measured, so the mechanism remains inferred rather than observed.
The results are narrow but clear. The smell of chocolate, especially dark and bitter chocolate, can help someone exercising on an empty stomach perform more repetitions without feeling overworked. It remains an open question whether chocolate is special or just one of many familiar scents that could work.
“We do not believe that chocolate is entirely unique, although it is a food signal with incredibly strong, widely recognized associations tied to feelings of reward,” said Naharrudin.
If other appealing food scents prove to have the same effect, the benefit may be small but real. A familiar food smell before a hard set could become another low-cost tool for training on an empty stomach.
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