Coffee drinkers may have more muscle and less body fat than non-drinkers, according to a growing body of research, although scientists stress that the findings show an association rather than proving that coffee itself causes these differences.

A recent study of 15,457 Korean adults found that people who consumed coffee more frequently tended to have more favourable body composition measurements. The researchers used data from the Korea National Health and Nutrition Examination Survey and assessed body composition using dual-energy X-ray absorptiometry, a method that can distinguish between fat mass and lean mass.

Among women in the study, those who reported drinking coffee three times a day had slightly lower fat mass and higher appendicular skeletal muscle mass and lean body mass than women who drank coffee less than once a day. Among men, drinking coffee three times a day was associated with higher measures of skeletal muscle and lean body mass, although the relationship with fat mass was less clear.

The findings add to previous research exploring a possible relationship between coffee consumption and muscle health. A 2024 population-based study involving 8,333 US adults found that higher consumption of coffee, caffeinated coffee and caffeine was associated with greater skeletal muscle mass after researchers adjusted for a range of other factors. However, the association disappeared among participants with a BMI above 30, highlighting the complexity of the relationship between coffee, body composition and other health factors.

Another study, known as the WASEDA’s Health Study, looked at 2,085 adults aged between 40 and 87. Researchers found that the prevalence of low muscle mass was lower among participants who reported drinking coffee more frequently. Those drinking two or more cups a day had a lower observed prevalence of low muscle mass than people drinking less than one cup a week. The researchers nevertheless described their findings as an association, rather than evidence that coffee directly prevents muscle loss.

There may also be a connection between caffeine and physical performance. A systematic review and meta-analysis published in the Journal of the International Society of Sports Nutrition found that caffeine consumption produced small improvements in maximal muscle strength and power in the studies examined. The researchers found a statistically significant effect on overall strength and power, although the effect was not consistent across every type of exercise.

A separate umbrella review examining 21 meta-analyses also found evidence that caffeine can improve several aspects of exercise performance, including endurance, muscle strength, muscle endurance and power. However, the researchers rated the overall quality of evidence as generally moderate, with some outcomes supported by lower-quality evidence.

That distinction is important because drinking coffee and taking caffeine in a controlled research setting are not necessarily the same thing. Coffee contains hundreds of compounds, including polyphenols and chlorogenic acids, meaning researchers cannot automatically attribute any observed differences in body composition to caffeine alone.

Lifestyle factors could also help explain the results. People who regularly drink coffee may differ from non-drinkers in their physical activity, diet, sleep, occupation and other habits. Most of the studies examining coffee and body composition are observational or cross-sectional, meaning researchers measure what people consume and how their bodies differ at a particular point in time. Such studies can identify patterns but cannot establish cause and effect.

In fact, research is not completely consistent. An earlier Korean study involving 6,906 adults found that lighter coffee consumption was associated with a lower likelihood of sarcopenia in men, while frequent consumption was associated with higher measures of obesity among women.

So, while the headline that coffee drinkers have more muscle and less body fat is supported by some intriguing research, it should not be interpreted as proof that coffee builds muscle or burns body fat. The evidence points to an interesting association that researchers are still trying to understand.

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