Scientists at the University of Malaya in Kuala Lumpur have discovered that smelling dark chocolate before lifting weights allows gymgoers to complete significantly more repetitions without making the workout feel any harder.
In the study, volunteers who sniffed dark chocolate right before tackling leg extensions completed around 18 extra repetitions compared to participants who smelled plain water.
Researchers believe the aroma tricks the brain into feeling fuller, allowing gymgoers to focus more on exercise and less on hunger. The effect was so pronounced that even milk chocolate provided a performance boost, although not as much as its darker counterpart.
Senior author Dr Mohamed Nashrudin bin Naharudin, from the University of Malaya, said the findings highlight the surprising power of smell to influence both body and mind.
"Exposing moderately trained men to chocolate odours right before and between sets of resistance exercise significantly increased their overall training volume without increasing their perceived exertion," Dr Nashrudin bin Naharudin said.
"Seeing a substantial increase in repetitions without the athletes feeling like they were exerting themselves any harder is a fascinating psychobiological outcome," he added.
For the study, published in the journal Frontiers in Physiology, researchers recruited 23 healthy men in their early to mid-20s and divided them into three groups.
None of the gymgoers had eaten for the ten hours prior to the test. Each group sniffed one of three liquid odour samples: liquified dark chocolate containing 90 per cent cocoa, liquified milk chocolate containing 60 per cent cocoa, or a water sample that acted as a control.
All participants performed leg extensions, which involve sitting down and extending the lower legs to lift a weight, in sets of ten repetitions with 3.5-minute rest intervals.
"Sniffing a 90 per cent dark chocolate odour added about 18 more repetitions to participants' leg extensions," Dr Nashrudin bin Naharudin said. "A 60 per cent milk chocolate odour added about nine repetitions compared to the water control."
Appetite and Psychological Cues
Levels of hunger, fullness, desire to eat, and plans to eat in the near future were assessed before the study and 30 seconds after the odour sample had been sniffed.
Overall, sniffing dark chocolate consistently led to people reporting less hunger, reduced desire and intention to eat, and greater fullness before exercise.
Across both types of chocolate, gymgoers managed more exercise repetitions without feeling as though they were training harder. The researchers suggested the changes in appetite perception could be related to what people learn about smells from a young age, as anticipating a food might have similar effects to when it is actually eaten.
"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," Dr Nashrudin bin Naharudin added.
"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."
Although it has not been tested yet, the research team believes other appealing foods could also have a performance-enhancing effect.
"We don't think chocolate is entirely unique, though it is a food cue with incredibly strong, universally recognized reward associations," Dr Nashrudin bin Naharudin concluded. "Although this hasn't been tested yet, other foods strongly linked to satiety could show similar effects. A person likely needs to find the odour familiar and appealing - or at least not repulsive - to trigger the psychological shift in appetite that's needed to see a performance boost."
Temperature and Sensory Impact of Chocolate
The findings build on wider research into how chocolate affects human senses and psychology. Last month, scientists settled another longstanding debate surrounding chocolate storage.
Professor Charles Spence, Professor of Experimental Psychology at the University of Oxford, explained that chocolate tastes better when kept in the fridge rather than the cupboard.
Chilling chocolate boosts both its flavour and texture, according to Professor Spence. "We like foods when they make some noise. One of the benefits of putting chocolate in the fridge is that you get a better snap when you break a fridge-cold bar," he said.
Health Benefits and Brain Chemistry
Chocolate is one of the world's most popular dietary vices, and extensive scientific research over many years suggests it offers multiple physical and psychological health benefits.
Researchers at Harvard University studied 8,000 men aged over 65 and found that those who ate modest amounts of chocolate lived almost a year longer than those who ate none.
In another study, Dr Neil Martin of the Cognition and Research Centre at Middlesex University exposed people to different smells and measured their brain activity. The results showed that smell receptors in the nasal passages reacted so strongly to the chemical mix in chocolate that it left participants on an emotional high.
Dark chocolate is also rich in essential minerals. A 100g bar of dark chocolate provides 2.4mg of iron and 90mg of magnesium, supplying around one third of the recommended daily intake for both nutrients.
White chocolate, by contrast, contains no cocoa solids, consisting only of cocoa butter, and is relatively high in fat. A 100g white Toblerone bar contains 540 calories and 30.7g of fat.
Despite its sugar content, dentists report that chocolate is less damaging to teeth than many other sweets because it tends to be chewed quickly rather than sucked. Naturally occurring tannins in chocolate also help inhibit the growth of dental plaque.
Additionally, a substance called phenylethylamine (PEA) is present in all chocolate. PEA is produced naturally by the brain and is thought to increase levels of mood-enhancing chemicals, including serotonin and endorphins. In theory, consuming more PEA increases feelings of affection and arousal, contributing to chocolate's reputation as an aphrodisiac.
The Food Network television series Food: Fact or Fiction? examined how eating chocolate affects the brain, highlighting findings that sharing chocolate with a loved one increases oxytocin levels. Chocolate also stimulates the release of beta-endorphins via PEA, which stokes the production of dopamine and norepinephrine, the chemicals associated with loving feelings. Furthermore, chocolate contains theobromine, a compound chemically similar to caffeine that stimulates the central nervous system and enhances mood.
