Does Coffee Change Your Body Composition? What a Large Finnish Study Found About Fat, Muscle and Metabolic Markers

A 2026 study from the University of Oulu found that middle-aged Finns who drank five or more cups of coffee per day had approximately 3.3 percentage points less body fat, around 2.3 kilograms more skeletal muscle, and meaningfully lower visceral fat than those drinking one to two cups — even though both groups had nearly identical body mass index scores of roughly 26.8. Published in the European Journal of Nutrition, it is one of the largest observational analyses to date linking habitual coffee intake to body composition and hormonal markers simultaneously, and it raises questions that go well beyond the familiar caffeine-and-alertness story.

Before examining what the study can and cannot tell us, here is a snapshot of the key body-composition figures reported across coffee-consumption groups:

Measure	Low consumers (1–2 cups/day)	High consumers (≥5 cups/day)	Difference
Average BMI	26.87	26.79	−0.08 (negligible)
Body fat percentage	30.40%	27.14%	−3.26 percentage points
Total fat mass	24.51 kg	22.17 kg	−2.34 kg
Visceral fat area	108.57 cm²	102.52 cm²	−6.05 cm²
Skeletal muscle mass	30.17 kg	32.46 kg	+2.29 kg
Waist circumference	92.24 cm	92.09 cm	−0.15 cm (negligible)

Source: Scandinavia Standard analysis of the Northern Finland Birth Cohort 1966 data

The table illustrates the study's central puzzle: two groups that look almost identical on the BMI chart diverge noticeably when you look inside at how weight is distributed between fat and muscle. That divergence is what makes the findings worth examining carefully — and what makes the study's limitations equally important to understand.

What exactly did the Finnish researchers study?

The study is an observational, cross-sectional analysis drawing on the Northern Finland Birth Cohort 1966, one of the most ambitious longitudinal health projects in Europe. The cohort enrolled nearly every child born in the provinces of Oulu and Lapland during 1966; the data used here were collected in 2012, when participants were all approximately 46 years old.

That uniform age is methodologically significant. Body fat percentage and skeletal muscle mass both shift substantially across the lifespan, so a study spanning a wide age range would struggle to separate coffee effects from age effects. Here, age was essentially held constant across all 2,264 participants, removing one major source of confounding as noted by ScienceDaily's coverage of the University of Oulu release.

Coffee intake was self-reported via a postal questionnaire. Participants fell into four broad groups: 70 reported drinking no coffee, 296 reported one to two cups per day, 822 reported three to four cups, and 1,076 reported five or more. Filter coffee was by far the most common preparation method among those who specified. One important caveat flagged by Scandinavia Standard is that the questionnaire did not define cup size, bean type, roast level, or what participants added to their coffee. Five small Finnish filter coffees and five large, sweetened café drinks would register identically in the data despite representing very different nutritional exposures.

The research team examined how habitual coffee consumption correlated with circulating metabolites, cardiometabolic risk markers, and sex hormone levels — a broader scope than most prior coffee studies, which tend to focus on a single outcome.

Why does the BMI paradox matter?

BMI is a person's weight in kilograms divided by the square of their height in meters, and it is widely used as a proxy for body fatness in population research. The Finnish study's most striking methodological contribution is demonstrating how thoroughly BMI can mask differences in body composition.

The low-consumption and high-consumption groups had average BMIs of 26.87 and 26.79 respectively — a difference so small it is clinically meaningless. Yet beneath those near-identical numbers, the estimated internal composition differed by more than three percentage points of body fat and over two kilograms of skeletal muscle. Visceral fat — stored around internal organs and most strongly associated with cardiometabolic risk — was also lower in the high-consumption group.

This matters beyond coffee research. It is a concrete illustration of why researchers increasingly argue that BMI alone is an insufficient tool for assessing metabolic health. Two people can sit at the same point on a BMI scale while their actual risk profiles differ substantially. The Finnish cohort, because of its size and uniform age, gives that argument unusually clean data to stand on.

What were the metabolic marker findings?

Higher coffee consumption was associated with lower circulating concentrations of branched-chain amino acids (BCAAs) in both men and women. BCAAs — leucine, isoleucine, and valine — are normally discussed in the context of muscle protein synthesis and sports nutrition. When chronically elevated in the bloodstream, however, they have been linked in prior research to insulin resistance and a greater risk of developing type 2 diabetes, as reported by News-Medical.net.

The mechanism behind elevated circulating BCAAs and insulin resistance is not fully resolved. One leading hypothesis is that impaired BCAA catabolism — the body's ability to break down these amino acids — is both a marker and a potential contributor to metabolic dysfunction. If coffee consumption is genuinely associated with lower circulating BCAAs, that could represent one pathway through which habitual coffee drinking relates to the reduced type 2 diabetes risk observed in earlier epidemiological work.

The glucose-insulin profile in men who drank more coffee was also described as more favorable, though the study did not specify exact fasting glucose or insulin values in the sources available. These metabolic associations persisted after the researchers adjusted for BMI and lifestyle factors — suggesting the hormonal and metabolic patterns are not simply a byproduct of coffee drinkers happening to weigh less or exercise more.

What did the study find about sex hormones?

The hormonal findings are the most novel aspect of the research, and they differed meaningfully between men and women.

In men, higher coffee consumption was associated with higher concentrations of total testosterone, higher bioavailable testosterone, and greater levels of sex hormone-binding globulin (SHBG). Free testosterone and the free androgen index were modestly lower. That combination — higher total and bioavailable testosterone alongside higher SHBG but lower free testosterone — reflects the fact that SHBG binds to testosterone in the bloodstream, reducing the freely circulating fraction while affecting how much reaches tissues in bioavailable form. The net clinical significance of this particular hormonal pattern is not yet established.

In women, the hormonal associations were less extensive. Higher coffee consumption was primarily linked to increased SHBG and lower measures of free androgens, without the same breadth of differences seen in men.

Lead author Luca Verroest, a Doctoral Researcher at the University of Oulu, described the findings this way: "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."

The persistence of the hormonal signature after adjusting for BMI and lifestyle factors is what makes the finding interesting rather than merely expected. Coffee drinkers in the cohort were more likely to be male and more likely to smoke — two variables that independently affect hormone levels and body composition. The associations surviving that adjustment gives them more credibility, though it does not eliminate the possibility that unmeasured variables are responsible.

Could hormonal pathways explain coffee's broader health links?

This is the speculative but scientifically plausible part of the story. Prior research has consistently associated habitual coffee consumption with a reduced risk of type 2 diabetes and cardiovascular disease, but the biological mechanisms have remained poorly understood. The Finnish team suggests that hormonal pathways — specifically the testosterone and SHBG associations — could be part of the explanation.

SHBG is a glycoprotein produced primarily in the liver that binds to sex hormones and regulates their bioavailability. Higher SHBG levels have been associated in other research with lower insulin resistance and a reduced risk of type 2 diabetes, independent of sex hormone levels themselves. If coffee consumption reliably raises SHBG, that could represent a hormonal mechanism connecting habitual coffee drinking to metabolic protection.

This remains a hypothesis rather than an established mechanism. The study is observational, which means it identifies associations but cannot determine whether coffee caused the hormonal differences, whether people with certain hormonal profiles are more likely to drink coffee, or whether a third variable drives both. The researchers are currently investigating these questions in animal models, with the longer-term goal of moving toward human intervention trials, according to the University of Oulu.

A separate 2024 randomized crossover study published in Nutrients and available via PubMed Central found preliminary evidence that coffee rich in phenolic compounds may improve body composition in people with overweight or obesity. Small in scale, it nonetheless points in a similar direction and suggests that specific coffee compounds rather than caffeine alone may be relevant. Phenolic compounds in coffee include chlorogenic acids, which have been studied for their effects on glucose metabolism and fat oxidation.

Why is Finland a particularly useful setting for this research?

Finland is one of the world's highest per-capita coffee-consuming countries, with average annual consumption of approximately 11.8 kilograms (about 26 pounds) per person. That figure reflects a deeply embedded cultural habit that produces a population with a wide and relatively stable range of coffee intakes, making it easier to detect associations that might be diluted in lower-consuming populations.

The Northern Finland Birth Cohort 1966 adds to this advantage by providing decades of follow-up data on a geographically defined population, with detailed health measurements collected at multiple time points. The 2012 data collection included body composition measurements that go beyond simple weight and height — a resource that many large cohorts lack.

The combination of a high-coffee-consuming population, a narrow age range, and detailed body composition data makes this cohort unusually well-suited to the question the researchers were asking. That does not make the findings definitive, but it does mean the study is better positioned than most to detect real signals if they exist.

What are the main limitations readers should know?

Several limitations deserve direct acknowledgment rather than footnote status.

The cross-sectional design is the most fundamental. When exposure and outcome are measured at the same point in time, it is impossible to establish which came first. People with naturally higher muscle mass and lower body fat may simply be more inclined to drink coffee, or more capable of tolerating higher caffeine intakes without sleep disruption. The data cannot rule this out.

The coffee-intake measure is self-reported and imprecise. As noted earlier, cup size, preparation method, and additives were not standardized. The 70 non-drinkers in the cohort are also a small group, limiting the ability to make strong comparisons between drinkers and non-drinkers.

The composition of the high-consumption group also differed from the low-consumption group in ways that matter. Men made up 35% of the low-consumption group but 55% of the high-consumption group, according to the Scandinavia Standard analysis. Men on average carry more skeletal muscle and less body fat than women, which means the raw group averages partly reflect sex differences rather than coffee effects. The adjusted regression models account for this, but residual confounding from unmeasured variables remains possible.

The cohort is also ethnically homogeneous — predominantly Finnish — which limits how far the findings can be generalized to populations with different genetic backgrounds, dietary patterns, or coffee-preparation habits.

Medical News Today's coverage and the Medical Dialogues video summary both emphasize the observational nature of the findings and the need for controlled human trials before any dietary recommendations could be shaped by this research. The study does not tell anyone how much coffee to drink.

What compounds in coffee might be responsible?

The study identifies associations but does not isolate the active compounds. Coffee is a chemically complex beverage containing caffeine, chlorogenic acids, diterpenes (cafestol and kahweol), trigonelline, and hundreds of other bioactive molecules. Different preparation methods extract these compounds in different proportions — filter coffee traps most of the diterpenes in the paper filter, while espresso and French press allow them through.

Caffeine is the obvious candidate for metabolic effects, given its well-documented influence on thermogenesis and fat oxidation in short-term studies. Chlorogenic acids have attracted growing research attention for their effects on glucose metabolism, and the 2024 Nutrients study on phenolic-rich coffee found body-composition signals in a controlled setting that suggest non-caffeine compounds may be doing meaningful work.

The Finnish researchers are currently using animal models to investigate which compounds drive the biological patterns they observed. That work, if it proceeds to human intervention trials, would be the next meaningful step toward understanding whether the associations in the Finnish cohort reflect a genuine causal relationship.

What does this mean for how you think about your daily cup?

The honest answer is: not much has changed in terms of actionable guidance. The Finnish study adds a detailed and well-designed data point to a growing body of evidence suggesting that habitual coffee consumption is associated with favorable metabolic patterns. It does not establish that drinking more coffee will reduce your body fat, increase your muscle mass, or improve your hormone profile.

What it does suggest is that the biological story of coffee is more complicated than caffeine and alertness. The hormonal signature — particularly the SHBG and testosterone associations in men — is a finding that prior research had not documented at this scale or with this level of adjustment for confounders. That makes it worth watching as the field moves toward intervention studies.

The metabolic benefits associated with coffee in observational research are generally attributed to habitual, moderate-to-high consumption of minimally sweetened coffee. The body-composition associations in the Finnish cohort were strongest in the five-or-more-cups group, but that group appears to have been drinking predominantly filter coffee — a preparation that differs substantially from heavily sweetened or cream-laden drinks that happen to contain espresso.

If you are interested in how other brewed beverages relate to metabolic health and sleep, the site's guides on caffeine-free herbal teas for sleep and herbal teas for digestion cover the complementary side of the brewed-beverage space — relevant if you are managing caffeine intake while still wanting functional benefits from what you drink.

The Finnish study's most durable contribution may be methodological rather than prescriptive: it demonstrates that BMI is a poor proxy for the body-composition differences that matter most for metabolic health, and that large, well-characterized cohorts can detect hormonal signals that smaller studies miss. Those are useful reminders regardless of how the coffee-causation question eventually resolves.

Randomized controlled trials in humans will be necessary before the findings can inform dietary recommendations, as the University of Oulu team explicitly acknowledges. Until that evidence exists, the Finnish data are best understood as a compelling hypothesis generator rather than a mandate to brew a fifth cup.