A large study finds sex-specific metabolic effects of habitual coffee: in men, higher coffee intake is linked to better fasting insulin and insulin levels, while in women the associations with glucose control are weaker or different.

Among men, higher coffee intake is associated with higher total testosterone and higher SHBG, but lower free testosterone and lower free androgen index, and these patterns persist after adjusting for BMI, education, smoking, activity, and alcohol use.

In women, higher coffee intake is associated with higher SHBG and lower free testosterone and free androgen index, indicating distinct hormonal effects by sex.

A major limitation is the cross-sectional design, which shows associations but cannot prove causation, and the study relied on self-reported coffee intake without details on cup size, brewing methods, or additives.

Participants reported daily coffee consumption from none to five or more cups, but cup size, brewing method, and additives were not specified.

Participants were grouped as none, 1–2, 3–4, or 5+ cups per day, with most consuming coffee and only a small fraction reporting no coffee.

Researchers note that causation cannot be established and some higher coffee intakes correlated with less favorable markers, including certain cholesterol particles and omega-3 levels, highlighting a complex picture.

Higher coffee intake is associated with lower levels of branched-chain amino acids (leucine, isoleucine, valine), which are linked to insulin resistance and diabetes risk, though causality is not proven.

Specifically, reductions in BCAAs with higher coffee intake were observed, but the study does not establish coffee as the cause.

Overall, the findings point to a distinct hormonal and metabolic profile associated with habitual coffee consumption, especially in men, but causality remains unproven and more long-term studies are needed.

A Finnish study of over 2,200 participants found regular coffee drinkers tended to have less body fat and more muscle mass compared with low or non-drinkers.

After fasting and a glucose challenge, higher coffee intake correlated with greater skeletal muscle mass, lower total fat and visceral fat, and a leaner body composition, while BMI stayed similar across groups.