Waist Size and Heart Disease: What Can BMI Miss?

What did researchers discover about waist size and heart disease?

The Cross-Cohort Collaboration analysis, published in the Journal of the American College of Cardiology in August, examined 260,959 adults across 15 cohorts. Researchers assessed nine outcomes, including heart attack, stroke, heart failure and atrial fibrillation. Among participants classified as having normal weight by BMI, 18% had a high waist-to-hip ratio. People with normal weight or overweight and elevated abdominal measurements had higher risks across most outcomes. [Original study](https://pmc.ncbi.nlm.nih.gov/articles/PMC13470613/)

The findings describe associations rather than proof that abdominal fat caused individual events. Researchers lacked information on physical activity, diet and genetic susceptibility to obesity, and waist measurements were assessed only once. These limitations matter: the study cannot establish how changing waist size would alter a person's risk or whether a measurement-based treatment strategy would prevent heart attacks. [American College of Cardiology study report](https://www.acc.org/about-acc/press-releases/2026/08/11/14/59/abdominal-fat-predicts-heart-disease-risk-better-than-bmi)

Why can abdominal fat reveal risk that BMI misses?

BMI cannot distinguish muscle from fat or describe fat distribution. Visceral fat surrounds internal organs, whereas subcutaneous fat lies beneath the skin. The American Heart Association identifies excess visceral fat as a cardiovascular risk marker and recommends considering abdominal measurements alongside BMI. This helps explain why two people with similar height and weight can have different health risks. [AHA scientific statement](https://pmc.ncbi.nlm.nih.gov/articles/8493650/)

A waist measurement remains an indirect indicator: it includes both abdominal fat beneath the skin and deeper fat, and cannot precisely separate them. It also does not diagnose blocked arteries or replace assessment of blood pressure, cholesterol, diabetes and smoking. Its practical value is to prompt a broader cardiovascular review when a person's BMI appears reassuring. [American College of Cardiology explanation](https://www.acc.org/about-acc/press-releases/2026/08/11/14/59/abdominal-fat-predicts-heart-disease-risk-better-than-bmi)

How can adults use waist measurements to improve prevention?

Measurement technique matters. NICE advises locating the bottom of the ribs and the top of the hips, placing a tape around the midpoint, and taking the reading after breathing out naturally. Its guidance recommends using waist-to-height ratio alongside BMI in adults whose BMI is below 35. Waist-to-height ratio divides waist circumference by height; it is different from the waist-to-hip ratio examined in the new study. Measurements should support clinical assessment rather than become a stand-alone diagnosis. [NICE obesity assessment guidance](https://www.nice.org.uk/guidance/ng246/resources/overweight-and-obesity-management-pdf-66143959958725)

Physical activity provides an established starting point for prevention. WHO recommends 150–300 minutes of moderate aerobic activity weekly, or an equivalent amount of vigorous activity, plus muscle strengthening on at least two days. People who are inactive can begin with shorter sessions and increase gradually. [WHO physical activity recommendations](https://www.ncbi.nlm.nih.gov/books/NBK566046/) Exercise and dietary changes can sometimes reduce abdominal fat even when body weight changes little, according to the American Heart Association. Progress can therefore include improved fitness and metabolic health alongside changes in waist size. [AHA evidence summary](https://newsroom.heart.org/news/more-belly-weight-increases-danger-of-heart-disease-even-if-bmi-does-not-indicate-obesity)