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The need for measuring waist circumference in the clinic stems in part from the limitations of body mass index . Layla Bird/Getty Images
  • A group of American Heart Association experts calls for measuring patients’ waist circumference to gauge their risk for cardiovascular disease.
  • The need for measuring waist circumference in the clinic stems in part from the limitations of body mass index (BMI).
  • BMI doesn’t show where the fat is located — which can affect a person’s health risks.

When trying to reduce your risk of obesity-related diseases such as cardiovascular disease or type 2 diabetes, monitoring changes in your weight seems like a good way to track progress.

But while stepping on a bathroom scale every day is easy, it may not provide the best snapshot of the health risks that come from carrying excess fat, in particular weight around the abdomen.

Instead, a group of experts recommends measuring waist circumference, alongside body mass index (BMI) — a combination of height and weight — as a way to identify people with a higher risk of cardiovascular disease.

“Recent data highlight abdominal obesity, as determined by waist circumference, as a cardiovascular disease risk marker that is independent of body mass index,” they wrote in a new scientific statement from the American Heart Association

The authors also called for doctors to routinely measure patients’ waist circumference, which may be especially helpful for patients trying to lose weight.

”Patients should have their BMI and [waist circumference] measured not only for the initial assessment of the degree of overweight and obesity,” wrote the authors, “but also as a guide to the efficacy of weight loss treatment.”

Some clinical guidelines already call for physicians to measure waist circumference alongside BMI to identify patients most at risk from being overweight or having obesity.

But Robert Ross, PhD, an obesity researcher at Queen’s University in Kingston, Ontario, Canada, says more needs to be done to ensure that waist circumference is measured routinely like other vital signs.

“We measure blood pressure on all patients,” he said. “Waist circumference is no harder to measure than blood pressure. Why can’t we take another 2 minutes and measure their waist?”

The need for measuring waist circumference in the clinic stems in part from the limitations of BMI.

For example, weightlifters with very low body fat are sometimes misclassified as overweight or obese when using BMI because they have a high amount of muscle mass for their height.

For other groups, BMI provides a relatively clear picture of a person’s overall body fat, but it doesn’t show where the fat is located — which can affect a person’s health risks.

People who carry a lot of weight around their abdomen — an apple-shaped body — have a higher risk of heart disease, type 2 diabetes, and premature death.

These health risks are lower for pear-shaped individuals, those who carry more weight around their hips and thighs.

“Premenopausal women tend to accumulate excess adiposity, or weight, in the lower body,” said Ross, “which, with respect to health risks, tends to be more benign.”

Using BMI along with waist circumference helps doctors differentiate between these two body shapes.

In addition, using BMI alone may not capture the health risks for older adults.

As people age, they tend to lose muscle mass, but they may also gain weight around the abdomen. So, even if their overall weight — and BMI — stays the same, they may shift toward a body shape associated with higher health risks.

Measuring waist circumference would capture the shift in fat distribution.

Several studies have looked at the link between waist circumference and diseases such as heart disease and diabetes.

Ross and his colleagues discuss many of these in a recent paper published in the journal Nature Reviews Endocrinology.

One of these studies found a strong connection between waist circumference and the risk of dying prematurely, regardless of BMI.

“For each one of the BMI units, as the waist circumference goes up, mortality risk goes up substantially,” said Ross, who was not involved in the study.

This was true even when researchers considered factors such as people’s smoking status, alcohol consumption, and physical activity.

In addition to estimating a person’s health risks, waist circumference can be used to track a person’s progress when they begin exercising regularly or improve their diet — something measuring weight alone might miss.

“We’ll hear from participants in our randomized trials all the time: ‘You know, the bathroom scale isn’t cooperating, but my dress fits better, my pants fit better,’” said Ross.

This change in waist size is not only a good indicator of improvements in health, it can also help people stay motivated.

“Instead of people feeling that they have failed in their attempts to address obesity, they are empowered,” said Ross. “Even though the bathroom scale may not be going down, or may not be cooperating as they had hoped, these other measures are improving.”