Coffee consumption linked to lower body fat and greater muscle mass, Finnish study finds

A study of more than two thousand Finns has found that people who drink coffee regularly tend to carry less fat on their bodies and maintain more muscle mass than their peers—even when they weigh the same. Researchers at the University of Oulu examined data from 2,264 people born in 1966 who were part of the Northern Finland Birth Cohort, comparing their coffee habits against detailed measurements of body composition, metabolic markers, and hormone levels. The findings suggest that coffee's effects on the human body extend well beyond the familiar jolt of caffeine-driven alertness.

The differences were striking in their specificity. People reporting higher coffee consumption had measurably less total body fat and less visceral fat—the dangerous kind that accumulates around organs. They also showed greater skeletal muscle mass. What made this particularly interesting was that these physical differences persisted even when researchers controlled for body mass index, meaning two people of identical weight could have very different fat-to-muscle ratios depending on how much coffee they drank. The study also found that higher coffee intake correlated with lower concentrations of branched-chain amino acids, compounds whose persistently elevated levels have been linked in previous research to insulin resistance and type 2 diabetes risk.

The hormonal picture proved equally complex, particularly among men. Those consuming more coffee showed what researchers described as a more favorable glucose-insulin profile—essentially better blood sugar control. They also had higher total testosterone and higher levels of sex hormone-binding globulin, a protein that regulates hormone availability in the bloodstream. Paradoxically, their free testosterone and free androgen index were lower, suggesting the hormonal changes work in concert rather than moving in a single direction. Women in the study showed fewer hormonal associations with coffee consumption, mainly an increase in sex hormone-binding globulin and lower measures of free androgens.

Luca Verroest, the doctoral researcher who led the work, noted the puzzle at the heart of their findings. "Coffee is consumed by millions of people every day, yet we still know surprisingly little about how it relates to our metabolism and hormones," he said. What caught the team's attention was the persistence of these hormonal signatures even after accounting for body mass index and lifestyle factors—and the fact that the patterns differed meaningfully between men and women. The researchers believe these hormonal changes may help explain why previous studies have found coffee drinkers face lower risks of metabolic diseases including type 2 diabetes, though they were careful to note that their work is observational and cannot prove that coffee itself causes these differences.

The research carries particular weight in Finland, one of the world's highest coffee-consuming nations where the average person drinks about 11.8 kilograms of coffee annually. The study, titled "Associations of habitual coffee intake with testosterone and cardiometabolic markers: the Northern Finland Birth Cohort 1966 study," was published in the European Journal of Nutrition. The researchers acknowledged a significant limitation: observational studies can identify patterns but cannot establish causation. They called for further research, including controlled intervention studies, to determine whether coffee directly produces these metabolic and hormonal changes and to identify which specific compounds in coffee might be responsible.