Two people can weigh about the same — and even have the same BMI — yet carry very different amounts of belly fat and muscle.
That matters, especially as we age.
Visceral fat — the fat packed around internal organs — is tied to insulin resistance, type 2 diabetes and heart disease.
Muscle, on the other hand, becomes increasingly important for strength, mobility and independence.
Now a large Finnish study has found one everyday habit linked to both: coffee drinking.
People who drank more coffee had less total body fat, less visceral fat and more skeletal muscle than lighter coffee drinkers — even though their average BMI was virtually the same.
That doesn’t mean coffee is a weight-loss treatment.
But it does add to an important message: healthy aging is about far more than the number on the bathroom scale.
The fat you can’t see matters
BMI uses height and weight to estimate whether someone falls into a healthy weight range.
It can be useful on a population level, but it cannot tell the difference between fat and muscle.
And it cannot tell you where fat is stored.
That’s important because visceral fat is more concerning than the softer fat just beneath the skin.
Visceral fat surrounds organs in the abdomen and is metabolically active. Higher amounts are associated with inflammation and a greater risk of cardiometabolic problems.
That’s why researchers from the University of Oulu looked beyond BMI.
They wanted to see how habitual coffee intake related to body composition, metabolic blood markers and sex hormones.
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The study included 2,264 adults from the Northern Finland Birth Cohort 1966. All were 46 years old when they completed questionnaires about their usual coffee intake and underwent clinical testing.
Nearly all were coffee drinkers.
Researchers divided them into four groups:
- Non-drinkers
- Low intake: one to two cups daily
- Moderate intake: three to four cups daily
- High intake: five or more cups daily
Same BMI, different body composition
The people who drank the most coffee had lower body-fat percentage, lower fat mass and less visceral fat.
They also had more skeletal muscle mass.
Yet BMI, waist circumference and waist-to-hip ratio were similar across the coffee groups.
That contrast may be the study’s most useful takeaway.
A stable weight does not necessarily mean your body composition is standing still — for better or worse.
The researchers measured body composition using bioelectrical impedance analysis, which estimates fat and muscle based on how a mild electrical current moves through the body.
It isn’t as precise as some imaging methods, but it is practical for large studies.
And the overall pattern was clear:
Higher habitual coffee intake was linked to a leaner body composition.
That muscle finding may matter even more with age, when preserving lean mass becomes increasingly important for strength, balance, mobility and independence.
Why might coffee affect body composition?
This study cannot prove that coffee caused the differences.
But the researchers point to several plausible explanations.
Caffeine can increase energy expenditure and stimulate thermogenesis — the process your body uses to produce heat and burn energy.
It may also increase fat oxidation, meaning the body uses more fat for fuel.
And coffee contains numerous bioactive compounds beyond caffeine that may influence metabolism.
Previous controlled studies have also found modest reductions in body fat with regular coffee intake.
That doesn’t mean adding extra cups will melt away belly fat.
But it does give researchers several biological pathways that could help explain why heavier coffee drinkers in this study had less fat despite having a similar BMI.
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The bloodwork pointed in the same direction
Higher coffee intake was also linked with lower blood levels of branched-chain amino acids, or BCAAs, in both men and women.
BCAAs are essential amino acids found in protein-rich foods.
Your body needs them.
But persistently elevated levels in the bloodstream have been associated with insulin resistance, type 2 diabetes, fatty liver disease and cardiovascular risk.
Among the men in the study, higher coffee intake was also linked with lower fasting insulin, lower insulin responses during a glucose-tolerance test and better estimated insulin sensitivity.
Taken together, the body-composition and blood-marker findings point toward an interesting metabolic pattern:
More habitual coffee drinking was associated with less visceral fat, more muscle and several markers of healthier glucose metabolism.
Again, these are associations.
But they are intriguing because visceral fat, muscle mass and insulin sensitivity are closely connected to metabolic health.
Coffee and testosterone: not a simple “boost”
The researchers also found differences in sex hormones.
Among men, higher coffee intake was associated with higher total and bioavailable testosterone, as well as higher levels of sex hormone-binding globulin, or SHBG.
But free testosterone — the fraction not bound to SHBG — was actually lower as coffee intake rose.
So this is not evidence that drinking more coffee will “boost testosterone” in a clinically meaningful way.
The hormone pattern was less pronounced in women.
Higher coffee intake was associated with higher SHBG and lower free testosterone, but not with higher total or bioavailable testosterone.
Interesting? Yes.
A reason to start drinking coffee for your hormones? No.
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What this means for your coffee habit
If you already enjoy coffee and it agrees with you, this study gives you another reason to appreciate it as part of an overall healthy routine.
But don’t start adding cups in hopes of losing visceral fat, building muscle or correcting hormone levels.
This was a cross-sectional study, which means researchers looked at coffee habits and health markers at one point in time. It cannot prove that coffee caused the differences.
Coffee intake was also self-reported, and the researchers did not have detailed information on cup size, roast, brewing method or what people added to their coffee.
So the findings are intriguing — but they’re not a prescription to drink five or six cups a day.
For most adults, up to 400 milligrams of caffeine per day is generally considered safe, although sensitivity varies.
Pay attention to how coffee affects your sleep, anxiety, heart rhythm and blood pressure.
And if cholesterol is a concern, filtered coffee may be a better choice than frequent unfiltered French press, boiled or Turkish coffee.
Sources:
Associations of habitual coffee intake with testosterone and cardiometabolic markers: the Northern Finland birth cohort 1966 study — European Journal of Nutrition
Associations of habitual coffee intake with testosterone and cardiometabolic markers: the Northern Finland birth cohort 1966 study — University of Oulu
Coffee drinkers have less fat, more muscle, and surprising hormone differences — Science Daily
Spilling the Beans: How Much Caffeine is Too Much? — Food and Drug Administration
Caffeine and cardiovascular disease — American Heart Association
FAQ: What coffee may mean for your metabolism
Can drinking coffee reduce belly fat?
The study found that people who drank more coffee tended to have lower total body fat and less visceral fat. However, the research was cross-sectional, so it cannot prove that coffee caused the difference or that drinking more coffee will reduce belly fat.
Does coffee increase muscle mass?
Higher habitual coffee intake was associated with greater skeletal muscle mass in the Finnish study. That does not mean coffee builds muscle by itself, but the finding is interesting because maintaining muscle becomes increasingly important for strength and independence with age.
How does coffee affect metabolism?
Coffee contains caffeine and other bioactive compounds that may influence energy expenditure, thermogenesis and fat oxidation. In the study, higher coffee intake was also associated with several metabolic differences, including lower BCAA levels and, in men, better measures of insulin sensitivity.
Can coffee improve insulin sensitivity?
Among the men in the study, higher coffee intake was linked to lower fasting insulin, lower insulin responses during glucose testing and better estimated insulin sensitivity. These findings show an association rather than proof that coffee directly improves insulin sensitivity.
How much caffeine is safe each day?
For most healthy adults, the FDA says up to 400 milligrams of caffeine per day is not generally associated with negative effects. Individual sensitivity varies, particularly when it comes to sleep, anxiety, heart rhythm and blood pressure.
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