Measuring waist circumference can help predict Type 2 diabetes risk

Want to gauge your risk for developing Type 2 diabetes? Don’t just step on the scale — reach for a measuring tape too, a new study suggests.

The circumference of your waist can tell you a lot about your chances of getting diabetes, according to a study published Tuesday in the journal PLoS Medicine. Health providers usually rely on body mass index to determine patients’ diabetes risk, but adding waist circumference to the equation would make those predictions more adequate.

Body mass index, or BMI, is the primary statistic used to gauge overall fatness. The formula — weight (in kilograms) divided by height (in meters) squared — doesn’t make any distinction between different kinds of fat, although researchers believe that visceral fat in the abdomen has the strongest link to diabetes.

And that’s where waist circumference comes in. The WC measurement is made either at the narrowest point of the torso or halfway between the lower ribs and the top of the hips. Obviously, this captures abdominal fat and is not influenced by subcutaneous fat in the arms, thighs or elsewhere.

For men, a “normal” WC is anything less than 34.6 inches, a “moderately increased” WC is between 34.6 and 40 inches, and a “large” WC is greater than 40 inches. For women, the cut-offs are 31.5 inches for a “normal” WC, 31.5 to 35 inches for a “moderately increased” WC and greater than 35 inches for a “large” WC.

European researchers looked at data on 340,234 people who were tracked for a total of nearly 4 million person-years as part of a large, multi-country study called InterAct. Half of the men were overweight (BMI between 25 and 29.99), and another 16.4% were obese (BMI greater than 30); among women, 33.8% were overweight and 15.8% were obese. In the entire group, 12,403 people developed Type 2 diabetes during the course of the study.

Compared with men whose BMIs were normal, men classified as overweight were 2.84 times more likely to develop diabetes and men who were obese were 7.58 times more likely to get the disease. Among women, those who were overweight were 3.81 times more likely to become diabetic and those who were obese were 11.6 times more likely to develop the disease.

The relative risks were very similar when using WC, the researchers found. Compared with men with normal WCs, those with “moderately increased” waists were 2.40 times more likely to develop diabetes and those with “large” waists were 7.58 times more likely to meet the same fate. For women, the corresponding risk figures were 3.02 for those with “moderately increased” waists and 11.6 for those with “large” waists.

The researchers concluded that WC could be used to predict diabetes risk independent of BMI. But they went on to say that the tool was most valuable when used in conjunction with BMI — especially for the large group of people who are overweight.

People whose BMIs are in the healthy range don’t need to worry much about diabetes risk, and those who are obese should be concerned regardless of their waist circumference, the researchers said. But for the large group of people who are overweight, taking WC into consideration could help doctors determine which patients need the most help to prevent diabetes.

“In terms of absolute risk, 7% of men and 4.4% of women who were overweight and had a large WC at baseline developed diabetes over a 10-year period, placing them at an absolute risk equivalent to or higher than that of obese participants,” the researchers concluded.

You can read the study online here.

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