A Finnish study of more than 2,000 middle-aged adults found that people who drank more coffee tended to carry less body fat, more skeletal muscle, and showed distinct hormonal patterns compared to lighter coffee drinkers, even when their body mass index was similar.
Researchers at the University of Oulu analyzed data from 2,264 people who were 46 years old and participating in the Northern Finland Birth Cohort 1966. The team examined how each participant's usual coffee intake related to circulating metabolites, markers of cardiometabolic risk, and sex hormone levels. The findings were reported by Science Daily.
People who consumed more coffee had lower levels of total body fat and visceral fat, the fat that accumulates around internal organs, along with greater skeletal muscle mass. Those differences appeared even though participants with higher and lower coffee consumption had comparable BMIs, meaning the changes in body composition were not simply explained by differences in overall body size.
Higher coffee intake was also associated with lower circulating concentrations of branched-chain amino acids in both men and women. When chronically elevated, those biomarkers have previously been linked to insulin resistance and a greater risk of developing type 2 diabetes. The finding adds another possible pathway through which coffee might be associated with reduced diabetes risk, which has been observed in earlier research.
Some of the clearest differences in the study appeared in men. Greater coffee consumption in male participants was associated with a more favorable glucose-insulin profile, higher levels of total and bioavailable testosterone, and greater concentrations of sex hormone-binding globulin, a protein that carries sex hormones through the bloodstream. However, free testosterone and the free androgen index were modestly lower among heavier coffee drinkers.
The hormonal associations were less extensive in women. Higher coffee consumption in female participants was mainly associated with increased sex hormone-binding globulin and lower measures of free androgens.
Luca Verroest, the study's lead author and a doctoral researcher at the University of Oulu, described the hormonal findings as particularly notable. "Coffee is consumed by millions of people every day, yet we still know surprisingly little about how it relates to our metabolism and hormones. 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," Verroest said.
Researchers noted that coffee has previously been associated with reduced risk of conditions including type 2 diabetes and cardiovascular disease, but scientists have not fully understood the biological processes that might explain those connections. The new findings suggest that changes in body composition, specific amino acid levels, and sex hormone patterns could each play a role.
The study was observational, meaning it identified associations between coffee intake and these health markers but did not establish that coffee directly caused the differences. All participants were the same age and drawn from the same geographic cohort, which allowed researchers to control for some variables but also limits how broadly the findings can be applied.
