A tape measure around the waist may tell doctors more about a person’s health than many people realize.
New research from Rutgers Health suggests that waist size can be a simple and useful way to identify unhealthy levels of body fat and the health risks that can come with it.
The study was led by Aayush Visaria of Rutgers Health and was published in JAMA Network Open.
Researchers wanted to know whether several body measurements are really needed to identify obesity, or whether simpler methods can provide nearly the same information.
Obesity is usually described as having too much body fat, but measuring body fat accurately is not always easy in an ordinary doctor’s office. For decades, doctors have commonly used body mass index, or BMI, which compares a person’s weight with their height.
BMI is quick and inexpensive, but it has important limits. It does not show where fat is stored, and it cannot always tell the difference between body fat and muscle, so people with the same BMI can have very different bodies and health risks.
Fat stored around the waist is particularly important because it is often linked with fat around internal organs. Higher amounts of this deeper abdominal fat have been connected with a greater risk of type 2 diabetes, heart disease, stroke and other health problems.
To examine different ways of identifying obesity, the Rutgers team studied data from about 1,900 U.S. adults between ages 20 and 59. The participants had taken part in the National Health and Nutrition Examination Survey, a major U.S. program that collects detailed information about people’s health and nutrition.
The researchers compared several ways of defining obesity with a highly accurate measurement of body fat. They also tested a newer obesity framework that combines several measurements, including BMI, waist size, waist compared with height, and waist compared with hip size.
The newer approach identified more people who had excess body fat. However, the Rutgers researchers found that much simpler methods performed almost as well when they tried to correctly identify obesity while avoiding incorrect diagnoses.
One of the best simple approaches was to consider either BMI or waist circumference. Waist circumference by itself also performed nearly as well, suggesting that a basic tape measurement can provide a surprising amount of useful information.
This matters in everyday health care because complicated measurements can be difficult to use regularly. Hip circumference, for example, is not commonly recorded during routine medical visits, while measuring the waist is relatively quick and requires little equipment.
The study also confirmed a weakness of relying only on BMI. BMI missed a meaningful number of people whose body-fat measurements placed them in the obesity range, which means someone can have a BMI that does not appear especially high while still carrying an unhealthy amount of fat.
Visaria said changes in clothing fit can sometimes provide an early clue. Needing to loosen a belt or buy larger pants is not a medical measurement, but a growing waist may be a useful reminder to check weight and waist circumference more carefully.
For individuals, the findings do not mean that waist size alone can diagnose every health problem. A person’s blood pressure, blood sugar, cholesterol, family history, fitness, age and other factors still matter when doctors assess the risk of diabetes and heart disease.
The study also has limits. It examined adults ages 20 to 59, so the results may not apply in exactly the same way to older adults, and measurements that work well for large groups do not perfectly predict the health of every individual.
Still, the findings make a strong practical case for bringing the tape measure back into routine health care. A method does not need to be complicated to be useful, and waist circumference may catch some people whose health risk would be overlooked if doctors looked only at BMI.
Overall, the study suggests that the simplest answer may sometimes be the most useful one. More research will be needed to see how well these approaches predict future illness, but combining weight with waist size could give patients and doctors an inexpensive way to notice unhealthy changes earlier and discuss steps that may lower long-term risk.
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