Millions of Americans who leave their annual physical exam with a clean bill of health — weight normal, BMI in range — may be walking around with cardiovascular risk that their doctor never measured and their scale will never show. A landmark study published Tuesday in the Journal of the American College of Cardiology provides the most powerful evidence yet that the single number used to determine whether most Americans are at healthy weight — body mass index — cannot see the specific kind of fat most strongly linked to heart attacks, strokes, and heart failure. A different measurement can. And unlike an MRI or a stress test, it requires nothing more than a cloth tape measure and sixty seconds.
The study, led by a team at the Johns Hopkins Ciccarone Center for the Prevention of Cardiovascular Disease, followed 259,388 people across 15 research cohorts for an average of twenty years. Researchers examined whether adding two waist-based measurements — waist circumference (WC) and waist-to-hip ratio (WHR) — to standard BMI classification changed the cardiovascular risk picture for individual patients. Across nine major cardiovascular outcomes including heart attack, stroke, heart failure, and atrial fibrillation, the answer was emphatically yes. For many patients, the two pictures looked nothing alike.
Why BMI Cannot See the Most Dangerous Fat
Body mass index is calculated by dividing weight in kilograms by height in meters squared, per the NHLBI clinical obesity guidelines. The formula was developed in the 1830s by Belgian mathematician Adolphe Quetelet — not as a clinical tool, but as a statistical method for describing population averages, as documented in a 2008 history of BMI. It was renamed “body mass index” in 1972 and formally adopted by the National Institutes of Health in 1985, per a complete BMI history
BMI’s fundamental limitation is one it was never designed to overcome: it cannot distinguish where fat is stored in the body, and it cannot separate fat tissue from muscle mass. Two individuals with identical BMI, height, and weight can carry their fat in entirely different places — and from a cardiovascular standpoint, that location is everything
The fat that accumulates deep inside the abdominal cavity — surrounding the liver, pancreas, and intestines — is known as visceral adipose tissue, and it behaves very differently from fat stored just under the skin, as detailed in a 2023 Frontiers cardiovascular review. Visceral fat is metabolically active in ways that subcutaneous fat is not. It secretes a range of adipokines — hormone-like molecules including leptin, resistin, and inflammatory cytokines — and it is particularly sensitive to the hormonal signals that trigger fat breakdown. When excess visceral fat breaks down, it releases free fatty acids directly into the portal vein, which drains straight into the liver. The result is a cascade of metabolic disruptions: elevated triglycerides, rising blood glucose, insulin resistance, and chronic low-grade inflammation — all of them established drivers of cardiovascular disease.
A person can carry substantial visceral fat and register a BMI that a clinic marks as normal. Their scale does not know where their fat is. But a tape measure around the waist can reveal it
What 260,000 People Over Two Decades Showed
The Cross-Cohort Collaboration, a research consortium that harmonizes data across multiple large long-term studies, provided the dataset that made this analysis possible at an unusual scale. Among the 259,388 participants, researchers measured waist circumference, waist-to-hip ratio, and BMI at baseline, then tracked their cardiovascular outcomes for an average of twenty years
The results exposed the scale of BMI’s blind spot. Among individuals whose BMI classified them as normal weight, 5% had a clinically elevated waist circumference and 18% had a clinically elevated waist-to-hip ratio, according to the ACC press release for the study. Among those classified as overweight by BMI, the proportions were even larger: 39% had elevated WC and 40% had elevated WHR. These individuals — unremarkable by the standard metric — faced 15 to 50 percent greater risk across most of the nine cardiovascular outcomes studied, compared with participants whose waist-based measures were in lower-risk ranges.
The findings complicated the picture from the opposite direction as well. Among participants with clinical obesity by BMI, 9% had a low waist circumference and 45% had a low waist-to-hip ratio. Those with obesity by BMI but low WC were not found to carry significantly elevated cardiovascular risk for most outcomes compared with normal-weight individuals who also had low WC — with one notable exception: for all-cause mortality, their risk was actually lower
“Indeed, it appears that WC and WHR reclassify risk defined by traditional BMI thresholds,” said Dr. Michael J. Blaha, MD, MPH, senior author of the study and director of clinical research at the Johns Hopkins Ciccarone Center. “We saw individuals with clinically determined normal weight who had elevated central adiposity and high WHR, associating them with higher risk across most outcomes.”
What the Cardiology Establishment Said
The findings drew an unusually direct response from the top of the cardiology field. Harlan M. Krumholz, MD, FACC — Editor-in-Chief of JACC and a professor at the Yale School of Medicine — published an editorial calling the study “enormously important.”
According to the American College of Cardiology press release, Krumholz wrote: “It is time to abandon a sole focus on body mass index. This enormously important study, based on data from hundreds of thousands of participants in large-scale cohort studies, authoritatively shows that waist circumference and waist-to-hip ratio provide critical information about cardiovascular risk, even among people with a BMI considered normal. Where fat is distributed matters, and these simple measures should be part of routine cardiovascular risk assessment.”
Lead author Dr. Zeina A. Dardari, PhD, MS, called the findings a mandate for clinical practice change. “Our findings emphasize the critical role of identifying elevated central adiposity, even in individuals with a normal BMI or with a BMI in the overweight range,” she said. “Relying solely on BMI may result in misclassification of cardiovascular risk across a wide range of cardiovascular outcomes. We encourage clinicians to consider central adiposity distribution across the entire BMI spectrum when evaluating cardiovascular risk in primary prevention settings.”
Why This Study Lands Now — and What It Changes
The debate over BMI’s limitations is not new. Critics have noted for decades that the metric was designed to describe populations rather than to diagnose individuals, that it conflates fat and muscle, and that it produces systematically different results across ethnic groups. But sustained criticism of BMI was not the same as a clinical consensus with a
That consensus has been building. In January 2025, the Lancet Diabetes & Endocrinology published a landmark Commission on the definition of clinical obesity — a formal international review that explicitly demoted BMI from primary diagnostic tool to screening measure and recommended that at least one waist-based measurement be added to confirm excess adiposity before a clinical obesity diagnosis is made. The Commission, detailed in the Lancet Diabetes & Endocrinology publication, distinguished for the first time between “preclinical obesity” (elevated risk, not yet producing organ dysfunction) and “clinical obesity” (a disease requiring treatment).
The JACC study published Tuesday is, in this context, the largest longitudinal evidence base yet supporting that institutional shift — demonstrating specifically what happens to patients over two decades when their central adiposity goes undetected by BMI
The study also connects to a phenotype that researchers have known about since 1981: “metabolically obese normal weight,” or MONW — individuals with healthy BMIs who nevertheless carry the metabolic profile of obesity. A paper in Applied Physiology, Nutrition, and Metabolism on the MONW phenotype characteristics helped establish the field, and a 2022 MDPI MONW prevalence review has estimated that MONW prevalence ranges from 5 to 45 percent of normal-weight individuals depending on measurement criteria, age, and ethnicity. Before this week’s study, the evidence base had been limited by smaller samples and shorter follow-up windows. A cohort of 259,388 people followed for twenty years changes that picture substantially.
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How to Read Your Own Risk Right Now
Neither waist circumference nor waist-to-hip ratio requires a lab, a prescription, or a specialist visit. Both can be measured at home with a flexible, non-elastic tape measure
For waist circumference, the standard measurement point used in clinical research — endorsed by both the National Heart, Lung, and Blood Institute and the World Health Organization — is the midpoint between the bottom of the lowest rib and the top of the iliac crest (hip bone), measured on relaxed exhalation with the tape horizontal and snug but not compressing skin, as specified in NHLBI measurement guidelines. Many people use the navel as a practical approximation; this is slightly less precise but widely used.
For waist-to-hip ratio, divide the waist measurement by the hip measurement taken at the widest point of the buttocks. The World Health Organization defines elevated cardiovascular risk thresholds for WHR as above 0.90 in men and above 0.85 in women
Current clinical thresholds for elevated risk, per the NHLBI obesity clinical guidelines, are a waist circumference above 102 cm (40 inches) in men and above 88 cm (35 inches) in women. Optimal cutoffs vary by sex, age, and ethnic background — research suggests lower thresholds may be appropriate for East Asian populations, for example — but for most American adults, the NHLBI figures are the clinical reference point
A 2019 meta-analysis of 72 prospective studies covering 2.5 million participants found that every 10 cm (about 4 inches) increase in waist circumference was associated with an 11 percent higher risk of all-cause mortality in men and 13 percent higher in women
What the Study Cannot Prove — and Why That Matters
The researchers are explicit about what this study does and does not establish. Because waist circumference and WHR were each measured only once — at the start of the follow-up period — the analysis cannot show how changes in abdominal fat over time influenced cardiovascular risk trajectories, according to the ACC press release. A person who reduced their waist circumference significantly over the twenty-year follow-up would still be classified by their baseline measurement
The dataset also lacked information on physical activity, diet quality, and genetic predisposition to obesity — all factors known to influence cardiovascular outcomes. Some of the associations the study found may reflect unmeasured factors correlated with waist size rather than abdominal fat itself
And as an observational study, the findings describe statistical associations, not established cause and effect. The study cannot prove that a person who reduces their waist circumference will directly reduce their risk of a future heart attack, though other lines of evidence support that link
On the measurement side, waist circumference and WHR are practical surrogates for visceral fat — not direct measurements of it. The gold standard for quantifying visceral adipose tissue is CT or MRI imaging, which accurately maps fat deposits by location but costs orders of magnitude more than a tape measure and is impractical for routine population-level screening. Two people with identical waist circumferences can have different amounts of visceral fat, depending on where their fat is distributed within the abdominal cavity.
What the combination of a very large sample, a twenty-year follow-up window, nine cardiovascular outcomes, and the statistical power of a multi-cohort analysis does provide is an evidence base robust enough to support a change in clinical practice — which is exactly what the paper’s authors and the JACC Editor-in-Chief are calling for
What Patients Should Do Now
The practical implication of this research is that waist measurement is available immediately. Both measurements are free, take roughly sixty seconds, and require no equipment beyond a standard tape measure. The thresholds are public and easy to apply
If your waist circumference exceeds 102 cm (40 inches) for men or 88 cm (35 inches) for women — or if your waist-to-hip ratio exceeds 0.90 for men or 0.85 for women — current evidence links that measurement to elevated cardiovascular risk regardless of what your BMI says. Those figures are not new; they have appeared in NHLBI obesity screening guidelines for decades. What is new, after this study, is the scale and duration of the evidence showing that the risk is real and that BMI alone misses it.
Patients who find themselves above these thresholds and have not had a cardiovascular risk conversation with a physician should ask for one — and specifically ask whether a more complete picture of central adiposity is part of their risk assessment. The study’s authors are calling on clinicians to make waist measurement standard practice. Until guidelines formally update, patients may need to ask for it themselves
Frequently Asked Questions
What is the difference between waist circumference and BMI for predicting heart disease?
BMI measures total body weight relative to height and cannot determine where fat is distributed. Waist circumference and waist-to-hip ratio measure abdominal girth and function as practical proxies for visceral fat — the metabolically active fat that accumulates around internal organs. Because visceral fat is linked to insulin resistance, chronic inflammation, and elevated cardiovascular risk in ways that subcutaneous fat (under the skin) is not, these waist-based measurements predict cardiovascular outcomes more accurately than BMI across most of the nine outcomes studied in the Cross-Cohort Collaboration’s 259,388-participant, 20-year dataset.
Can I have a high risk of heart disease even with a normal BMI?
Yes, according to this study. Among participants whose BMI classified them as normal weight, 18 percent had an elevated waist-to-hip ratio and 5 percent had an elevated waist circumference. Those individuals faced 15 to 50 percent greater risk for most of the nine cardiovascular outcomes measured — including heart attack, stroke, and heart failure — compared with participants whose waist measurements were also in the lower-risk range. A normal BMI, by itself, does not confirm that visceral fat is at a safe level.
What waist circumference measurement indicates elevated heart risk?
Current NHLBI clinical guidelines flag elevated cardiovascular risk at a waist circumference above 102 cm (40 inches) in men and above 88 cm (35 inches) in women, per the NHLBI obesity guidelines. The World Health Organization uses waist-to-hip ratio thresholds of 0.90 for men and 0.85 for women. These thresholds can vary by ethnicity — research suggests lower cutoffs may be appropriate for East Asian populations — and individual risk depends on other factors as well. A measurement above these thresholds is a reason to have a cardiovascular risk conversation with a physician, not an automatic diagnosis.
Why did it take so long for cardiology to move beyond BMI?
BMI’s limitations have been debated for decades, but the evidence base for a practical alternative was limited. The January 2025 Lancet clinical obesity Commission was a significant turning point, formally recommending that waist-based measurements accompany BMI in obesity assessment. What the Cross-Cohort Collaboration study adds is the largest longitudinal dataset yet — 259,388 participants over twenty years — to quantify precisely how much cardiovascular risk BMI-alone screening misses. That scale of evidence is designed to move clinical guidelines from debate to action.
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