Can Sniffing Chocolate Boost Gym Performance? Study Suggests Benefits, But Experts Urge Caution

Simply smelling chocolate can improve gym performance, according to a recent study that has attracted global attention.

The journal claimed: "Sniffing chocolate could make your leg day workout easier, even on an empty stomach." Headlines followed, including: "Sniff chocolate, do more reps without trying harder!" This came with the qualifier: "We're not even kidding. It's a psychobiology thing."

But does the evidence support these claims? An exercise scientist examined the findings and concluded that the results should be interpreted with caution.

How The Study Worked

The study involved 23 young men who had been doing resistance training at least twice a week for the past two years. Resistance training involves working muscles against a load, such as lifting weights, using machines or bodyweight exercises, The Conversation reports.

Participants visited the laboratory on three separate occasions after fasting overnight for about 10 hours. During each visit, they smelled one of three jars for 30 seconds in a random order: a 90% cocoa dark chocolate mixture, a 60% cocoa milk chocolate mixture, or plain distilled water, which served as the control.

They then performed leg extensions, completing as many sets of 10 repetitions as possible at 80% of their 10-repetition maximum. Between each set, they smelled the assigned jar again and continued until they could no longer complete another set.

What Researchers Found

Participants completed around 18 more repetitions after smelling dark chocolate and about nine more after smelling milk chocolate, compared with smelling water. According to the researchers, dark chocolate improved performance by more than 25%.

For comparison, previous studies have shown that caffeine generally improves resistance training by about one additional repetition per set, making the chocolate results appear unusually large.

Participants also reported that dark chocolate reduced feelings of hunger, while milk chocolate had no effect on hunger despite being rated as the more pleasant smell. The researchers suggested that hunger may compete for attention during exercise and that the aroma of dark chocolate could create a feeling of fullness, helping participants push harder. They also speculated that the familiar smell of dark chocolate may have contributed to the effect.

Why Caution Is Needed

The study has an important limitation. Although it was described as a double-blind trial, the control was plain water, which has no smell. As a result, participants could almost certainly identify when they were smelling chocolate rather than the control.

In addition, the main outcome measured was how many repetitions participants chose to perform before stopping. This reflects willingness to continue rather than physical performance alone. Knowing the purpose of the study may therefore have influenced the results.

The authors acknowledged these limitations and described the research as "exploratory". However, the exercise scientist argued that the conclusions were overstated and that the study does not provide enough evidence to conclude that smelling chocolate improves gym performance.

What Other Research Says

There is little research on smelling chocolate and exercise performance. However, studies have shown that hunger can reduce gym performance, while eating food, even low-calorie options such as no-calorie jelly, can improve it. This effect appears to be linked to having food in the stomach rather than the type of food consumed.

Most research on chocolate has focused on eating it rather than smelling it. Although dark chocolate contains flavanols that are believed to support exercise performance, studies have consistently found that eating chocolate before exercise does not improve results.

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