How a piece of string can tell you whether you're too fat

Study finds someone with a normal BMI can sometimes have a greater risk of heart disease than an obese person

Having a a bit of belly could be bad for your health, but is that always true? (Getty Images)

Everybody knows that having a a bit of belly -- or more -- could be bad for your health, but is that always true? According to new research, one way to answer that question is pretty simply: measure the broadest part of your waist and hips with a piece of string.

“If it takes more string to measure waist than hips that’s bad, and it relates to a higher rate of death,” said Francisco Lopez-Jimenez, a Mayo Clinic researcher and lead author on a study exploring the relationship between body mass index and weight distribution.

The study found that people with a normal body mass index but an apple-shaped torso (sometimes known as a dad bod) are at greater risk of dying from heart disease than an obese person with more evenly distributed weight.

For both men and women, the hips should have a longer circumference around the largest part of the buttocks, compared to the abdomen. A healthy ratio of belly-to-hips in women is .85-to-1, and for men the ideal ratio is .9-to-1. Lopez-Jimenez said any ratio greater than 1-to-1 is cause for concern.

It's well-known that BMI, based on a formula that takes into account height and weight but not muscle mass or overall level of fitness, has its limitations. But this new way of thinking -- and measuring -- health is another useful metric for people to use in determining whether a little extra girth is really that bad. Or whether you're actually a normal weight for your height, but have the kind of extra abdominal fat that poses higher health risks.

The following diagram shows a few of the different kinds of body shapes and what they mean for your health. The first kind--an average of a normal weight but with a bit of belly--is one of the deceptively perilous body shapes. Meanwhile, men with a high BMI but a low waist-to-hip ratio are often doing just fine. Think athletes.

A woman with a low BMI but a large stomach relative to her hips is at higher risk for health problems, while a woman with a high BMI but relatively small waist may be fine.

Darla Cameron/The Washington Post (Darla Cameron/The Washington Post)

“The measurement is so simple that I personally believe people should feel empowered to measure themselves, like they weigh themselves,” Lopez-Jimenez said. "You can't get simpler than that."

If your measurements are out of sync, don't despair: Lopez-Jimenez said a diet low in refined carbohydrates may help. Strength training and aerobic exercise are also key: “The very first fat that we burn after engaging in a good exercise program is actually abdominal fat."

He also cautions that people with abdominal obesity shouldn't try to increase their BMI on purpose. Some athletes have a high BMI — anything above 30 is generally a sign of obesity — but a healthy hip-to-waist ratio, because muscle weighs more than fat.

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