The National Heart, Lung, and Blood Institute puts a warning line right at the waistband. A waist wider than 40 inches (102 cm) in men, or 35 inches (88 cm) in women, raises the risk of heart disease and type 2 diabetes.
The scale can miss this. Two people with the same BMI can carry very different amounts of fat around the middle, and the middle is where the risk sits.
The problem is not the belt size itself but the visceral fat behind it. This deep fat wraps the liver, pancreas and intestines, and behaves differently from the softer layer just under the skin.
Framingham Heart Study data show that visceral fat is a stronger correlate of insulin resistance than the subcutaneous kind, even after adjusting for body mass index. That helps explain why waist size flags risk the scale does not.
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One cohort drew on 5,775 US adults from the National Health and Nutrition Examination Survey between 2001 and 2014, all classed as metabolically healthy, no diabetes, high blood pressure, high triglycerides, low HDL cholesterol or elevated fasting glucose. Participants were linked to the National Death Index for follow-up.
Each 10 centimeters (about 4 inches) of extra waist was linked to roughly an 8 percent higher risk of dying from any cause during follow-up.
The same analysis, published in Reviews in Cardiovascular Medicine in 2024, tied every 10-centimeter increase to a 1.45 times higher prevalence of cardiovascular disease.
Why location beats weight
Visceral fat is metabolically active. It releases inflammatory signals and free fatty acids into the portal vein that feeds the liver. That pushes the body toward insulin resistance, higher blood sugar and elevated triglycerides.
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A slim-looking person with excess belly fat can carry the same underlying pattern as someone with a much higher BMI.
Waist size is not the only shortcut. A waist wider than half your height is another quick screen, but the absolute waist number is the fastest one to check.
How to measure your waist in 30 seconds
Stand up straight with feet about hip-width apart. Wrap a flexible tape measure around your bare middle, just above the top of your hip bones. The tape should sit level, snug against the skin without pressing in.
Take the reading just after you exhale normally, as the NHLBI advises. For a more consistent number, take two or three measurements and use the average.
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A reading above the 40-inch or 35-inch threshold is not a diagnosis. It is a signal worth raising at your next appointment, especially if there is a family history of heart disease, type 2 diabetes or high blood pressure.
A clinician can pair the number with blood pressure, blood sugar and cholesterol to build a fuller picture.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.