The smell of dark chocolate helped the men do more reps in the gym

The most interesting thing is that they did not feel as though they were training any harder. The smell of dark chocolate was associated with reduced feelings of hunger, a reduced desire to eat and a greater sense of fullness.

The study was published in Frontiers in Physiology.

But the findings should be interpreted with caution. This is not advice to go to the gym on an empty stomach and sniff chocolate instead of eating. Only 23 young men took part in the study; there was just one exercise — leg extensions on a machine — and the mechanism behind the effect has not yet been proven.

Details

The researchers investigated whether the smell of food could affect not only appetite but also physical performance. To do this, they recruited 23 healthy, moderately fit men aged between approximately 18 and 26.

All participants had fasted for at least 10 hours prior to the experiment. They then performed leg extension exercises — sitting on a machine, lifting weights by extending their knees.

Before the exercise and between sets, the participants inhaled one of three samples: dark chocolate with 90 per cent cocoa, milk chocolate with 60 per cent cocoa, or odourless water as a control.

What happened

The scent of dark chocolate was associated with the best performance. Participants who smelled it completed approximately 18 more repetitions than in the control condition with water.

The smell of milk chocolate also led to an increase, but a smaller one — around 9 extra repetitions compared with the control.

However, the men did not report that the task had become more difficult. In other words, they were doing more work, but subjectively did not feel that they were exerting themselves more.

Why dark chocolate had a stronger effect

Dark chocolate does not just smell pleasant. In the experiment, it had a stronger effect specifically on appetite: after smelling it, participants felt less hungry, had less desire to eat and felt more full.

Milk chocolate was perceived as having a more pleasant smell, but did not reduce hunger as noticeably. The authors therefore suggest that these two smells may have worked in different ways.

Dark chocolate with a high cocoa content may have been perceived by the body as a signal of a ‘substantial’, satisfying meal. It seemed to create an anticipation of fullness in advance. Milk chocolate may have acted more as a pleasant stimulus, improving mood and making the workout more enjoyable.

How a smell can ‘trick’ hunger

The smells of food are closely linked to memory, emotions and appetite. If a person has eaten a particular food many times, the brain associates its smell with the expected consequences: taste, satiety and pleasure.

Therefore, the smell of food can trigger the body’s preparation for a meal even before a person has eaten anything. It is as if the body receives a signal: a meal is coming. This can alter the sensation of hunger and fullness.

In this study, the authors suggest that the smell of dark chocolate may have temporarily shifted the perception from hunger to satiety. And if hunger is less of a hindrance, exercising on an empty stomach may feel easier.

Limitations

The study was preliminary. The sample size was small — just 23 participants. All were men and had some experience of exercise. The results therefore need to be confirmed in larger groups.

The authors also did not measure hunger hormones, blood sugar levels, brain activity or digestive function. Consequently, the ‘tricking the hunger’ explanation remains a hypothesis for now.

Another point to note: the water in the control group was odourless. Participants may have realised they were in the control condition, and this can sometimes influence behaviour and expectations.

Why this matters

The study shows that smells can influence training not only through mood but also through appetite. This is particularly interesting for situations where a person is training on an empty stomach and hunger interferes with their ability to perform the exercise.

However, the practical implications are still very limited: the scent of dark chocolate may be an interesting sensory stimulus that is worth investigating further. It is not a substitute for nutrition, nor is it a sports supplement, nor is it a universal way to improve performance.

Background

Scientists have long known that the smells of food influence appetite. They can heighten the desire to eat, trigger memories, alter mood and even set in motion the anticipation of satiety.

However, the link between the smell of food, feelings of hunger and strength training has been little studied. This new study specifically examined this three-way relationship: smell – appetite – exercise performance.

Dark chocolate was not chosen at random. It has a strong, recognisable smell and is associated with a rich flavour and a dense texture. Therefore, it was likely to have a stronger influence on the anticipation of satiety than a neutral smell or water.

Source

Study: “Chocolate Odour Enhances Resistance Exercise Performance through Appetite Suppression in the Fasted State: An Exploratory Study”, Frontiers in Physiology, 2026.