A simple waist measurement performs almost as well as a full-body DXA scan at spotting the deep abdominal fat that drives heart disease and type 2 diabetes, while the standard BMI number misses roughly half of adults who actually meet a body-fat definition of obesity. That is the takeaway from a Rutgers Health analysis of 1,900 U.S. adults published in JAMA Network Open on August 7, 2026.
The finding matters because BMI, the height-to-weight ratio doctors have leaned on for decades, ignores where fat sits. Fat packed around the organs in the abdomen, known as visceral fat, is far more closely tied to cardiovascular and metabolic disease than fat stored just under the skin, according to a review in BMC Public Health. A waist tape captures that abdominal fat directly.
What the Rutgers team measured
The researchers pulled data from the National Health and Nutrition Examination Survey and compared five ways of screening for obesity against a dual-energy X-ray absorptiometry scan, the reference method that measures body fat directly. Obesity was defined as body fat of 25 percent or more in men and 35 percent or more in women.
BMI alone caught only 51.3 percent of adults who met that body-fat threshold. Waist circumference alone caught 71.4 percent. Using either an elevated BMI or an elevated waist measurement, whichever came first, pushed sensitivity to 74 percent while keeping specificity at 89.5 percent, according to the Rutgers press release and the Healio summary of the paper.
Also read: Sleeping under 7 or over 9 hours a night may leave hidden marks on your brain
Notably, the simple BMI-or-waist approach outperformed a newer, more complicated framework recently proposed by a Lancet commission that folds in waist-to-height and waist-to-hip ratios, according to Healio's reporting on the study. Hip circumference, which the Lancet framework requires, is rarely recorded during a routine clinic visit.
Where the risk line sits
The National Heart, Lung, and Blood Institute has long used a single, memorable cutoff for elevated risk of heart disease and type 2 diabetes: a waist wider than 40 inches (about 102 cm) in men and wider than 35 inches (about 88 cm) in women. That aligns with the 2007 consensus statement from the American Diabetes Association and The Obesity Society, which noted that waist circumference is often a stronger predictor of diabetes than BMI.
The NHLBI also spells out how to measure correctly. Stand up, place a tape around your middle just above the hip bones, and take the reading right after you breathe out. Do not suck in.
What it means in practice
"Pay attention to the need to loosen your belt or get bigger pants," Aayush Visaria, faculty at the Rutgers Health-RWJBarnabas Health Center for Climate, Health, and Healthcare and lead author of the study, said in the Rutgers announcement. "Although clothing size isn't the same as a proper waist circumference measurement, it can be an early sign of unhealthy amounts of body fat."
Also read: Colorectal cancer screening now starts at 45: what the 2026 guidelines say for you
If the tape reads above the NHLBI cutoff, that is not a diagnosis, but it is a signal worth bringing to a primary-care visit. The added value comes from pairing the number with routine checks the doctor can order, such as blood pressure, fasting glucose, and a lipid panel. As we reported earlier, a waist wider than half your height also flags heart risk that BMI can miss, giving readers a second at-home ratio to sanity-check the tape number.
Also read: If you have type 2 diabetes, starting statins early may lower your dementia risk
This article is made and published by Jesper Bengtson, who may have used AI in the preparation.