A young woman with a huge cup of coffee
People who drink more coffee may differ from lighter drinkers in how their bodies are built, even when they weigh the same. A large Finnish study found that, among people with a similar body mass index (BMI), coffee drinkers had less total and visceral fat, more skeletal muscle, lower levels of certain blood amino acids and a distinct sex-hormone profile. The fat, muscle and amino acid findings applied to both men and women. However, the study captured a single moment in time, so it shows an association, not proof that coffee causes these differences.
What you need to know
- The analysis included 2,264 participants from the Northern Finland Birth Cohort 1966, examined in 2012 at age 46.
- At similar BMI, coffee drinkers of both sexes had less total and visceral fat, more skeletal muscle and lower levels of branched-chain amino acids.
- Men who drank more coffee had higher total and bioavailable testosterone, but slightly lower free testosterone, alongside higher levels of the binding protein SHBG.
- The study was cross-sectional and coffee intake was self-reported, so it cannot show that coffee causes any of these differences.
Same weight, different bodies
BMI takes into account only weight and height. As a result, two people with the same BMI can have very different bodies: one may carry more muscle, the other more fat. Visceral fat is especially important, because it sits around the internal organs and is most strongly linked to metabolic problems.
This is where the Finnish researchers found a difference. Among people with a similar BMI, coffee drinkers had less total and visceral fat and more skeletal muscle, the muscles used for movement. This held for both men and women. To judge how seriously to take the result, it helps to look first at who was studied and how.
A country that drinks almost 12 kg of coffee per person a year
Coffee is among the most popular drinks in the world, and Finns drink more of it than almost anyone else: around 11.8 kg per person per year. That makes Finland a convenient place for this kind of research, because many people there drink coffee regularly and in large amounts.
A cup of hot coffee among coffee beans on a table
Who took part
The data came from the Northern Finland Birth Cohort 1966, a group of people born in 1966 who have been followed since birth. In 2012, when they turned 46, 10,331 cohort members were invited for an examination and 5,832 attended. The final analysis included 2,264 participants who had complete data on coffee consumption, body composition, blood tests and sex hormones.
The work was led by Luka Verroest of the University of Oulu. The paper was published in the European Journal of Nutrition on 16 July 2026 and was brought to a wider audience by the popular-science site RathBiotaClan.
The researchers were addressing a long-standing question. Coffee has already been associated with a lower risk of type 2 diabetes and heart disease, but why remains unclear. Data on coffee and testosterone, meanwhile, are scarce and contradictory.
Less fat and fewer “diabetes-linked” amino acids
Beyond fat and muscle, the researchers found another pattern in the blood. Coffee drinkers of both sexes had lower levels of branched-chain amino acids. These are building blocks of protein, but high blood levels of them have previously been linked to insulin resistance, a state in which cells respond poorly to insulin, and to a higher risk of diabetes.
In men who drank more coffee, blood sugar and insulin were also in a more favourable balance. But the most striking findings concerned hormones.
Higher testosterone in men, but not all of it
Men who drank more coffee had higher total testosterone and higher bioavailable testosterone, the portion the body can use more easily. Free testosterone, which is not bound to any proteins, was slightly lower. At first glance, that looks contradictory.
The picture makes more sense when sex hormone-binding globulin (SHBG) is taken into account. This protein binds hormones in the blood and holds them in reserve. Coffee drinkers had more of it. The simplest explanation is that there is more hormone overall, but a noticeable share of it is in bound form. The authors, however, did not test this mechanism.
In women, the picture was more modest: SHBG was also higher, and free male hormones (androgens) were lower. The associations reported are summarised below:
| Measure | Men | Women |
|---|---|---|
| Total and visceral fat | Lower | Lower |
| Muscle mass | Higher | Higher |
| Branched-chain amino acids | Lower | Lower |
| Total and bioavailable testosterone | Higher | Not reported |
| SHBG | Higher | Higher |
| Free androgens | Lower | Lower |
The table shows only the direction of each association. The description of the study does not say how large the differences were or how many cups a day are involved. According to Verroest, what surprised the researchers most was a clear “hormonal signature” that persisted even after adjusting for BMI and lifestyle.
Why coffee cannot yet be considered a remedy for excess fat
The main limitation is that this was a cross-sectional snapshot: every participant was examined only once. A study like this shows that two things occur together, but not that one causes the other. It is possible that healthier, more active people simply tend to drink more coffee, rather than the other way round.
A man at a table by the window with a cup of black coffee
There are other caveats as well:
- participants reported their own coffee intake; nobody measured it;
- Finland’s population is fairly homogeneous, so it is unclear whether the results would be repeated in other countries;
- coffee contains more than 1,000 compounds, and the study did not test which of them, if any, is responsible.
What comes next
The authors themselves describe hormones as only a possible piece of the puzzle: they may partly explain why coffee is associated with healthy metabolism. Animal experiments are now under way. Human trials are the next goal, and only after those will it be possible to offer any dietary advice.
For coffee lovers, the work offers a reason not to worry about the habit, but not a reason to double their daily cups in pursuit of muscle or testosterone. Clearer answers will come from controlled trials in which people are assigned a set amount of coffee and researchers track how their bodies change.
