People who drank more coffee had lower levels of body fat and visceral fat despite having similar BMIs.
Higher coffee intake was associated with differences in metabolism and sex hormones, particularly among men.
The study found associations, not proof, that drinking coffee directly causes these changes.
For many people, coffee is simply part of the morning routine. But new research from the University of Oulu in Finland suggests that how much coffee people regularly drink may be linked to several markers of metabolic health — and to differences in sex hormones.
The study found that people who reported drinking more coffee tended to have less total body fat and visceral fat, along with more skeletal muscle mass, even though their body mass index (BMI) was similar to that of people who drank less coffee. Higher coffee consumption was also associated with lower levels of certain branched-chain amino acids, which have previously been linked to insulin resistance and type 2 diabetes when chronically elevated.
"Coffee is consumed by millions of people every day, yet we still know surprisingly little about how it relates to our metabolism and hormones,” researcher Luca Verroest said in a news release. “What stood out in our findings was a distinct hormonal signature that didn't disappear even after we took into account BMI and lifestyle factors, with several of these associations differing between men and women.”
How researchers studied coffee drinkers
Researchers analyzed data from 2,264 people who were part of the Northern Finland Birth Cohort 1966. All of the participants were 46 years old when the data was collected in 2012, and 47% were men.
Participants reported how many cups of coffee they typically drank each day. Researchers grouped them into non-coffee consumers, people drinking one to two cups daily, moderate coffee consumers drinking three to four cups, and high coffee consumers drinking five or more cups per day.
The researchers then compared coffee consumption with measurements including body composition, blood glucose and insulin, cholesterol, metabolites, and sex hormones. They also adjusted their analyses for factors including BMI, education, smoking, alcohol consumption, and physical activity.
What the findings could mean for coffee drinkers
The researchers found some notable differences between people who drank more and less coffee.
In men, higher coffee intake was associated with a more favorable glucose-insulin profile, as well as higher levels of total and bioavailable testosterone and sex hormone-binding globulin (SHBG). At the same time, free testosterone and the free androgen index were somewhat lower.
Women showed fewer hormonal associations, although higher coffee consumption was linked with higher SHBG and lower measures of free androgens. The researchers also found that higher coffee consumption was associated with lower levels of branched-chain amino acids in both men and women.
There’s an important catch, though: This was a cross-sectional observational study, meaning researchers looked at existing patterns rather than assigning people to drink a certain amount of coffee. So the findings cannot establish that coffee itself caused the differences.
The researchers say future studies will need to determine whether coffee drives these changes and which compounds might be responsible.