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Daily Dose

Americans’ waistlines grow as obesity rates level off, study finds

Ask any woman what her waist size is, and chances are, she doesn’t have a clue. Unless she’s shopping in the men’s department, a woman doesn’t have a pants size that’s measured in waist inches. In fact, her size might not have changed much through the years -- even if her waist has expanded -- because clothing manufacturers have been cutting dress sizes bigger, to please those of us who don’t want to go up a size when we gain 10 pounds.

Perhaps as a result of this ignorance, the average American woman’s waist size has increased at a much faster rate than the average American man’s, according to a new study published Tuesday in JAMA, which examined federal health surveys conducted in nearly 33,000 Americans from 1999 to 2012. The study found a woman’s waist increased by 1.5 inches, while the average man’s increased by 0.8 inches.


Nearly 44 percent of men and 65 percent of women have what’s called “abdominal obesity,” which typically indicates an excess of metabolically active fat that interferes with proper functioning of the kidney, liver, and other organs. That compares to 37 percent of men and 55 percent of men who had abdominal obesity in 1999.

Such “apple-shaped” individuals — who have a waist size of 40 inches or greater for a man or 35 inches or greater for a woman — have a higher risk of diabetes, heart disease, and certain cancers compared to “pear-shaped” folks with smaller waists and larger hips.

(To get a proper waist measurement, place a tape measure around your body at the top of your hipbone — usually at the level of your belly button.)

Oddly, previous analyses using the same data have shown that the prevalence of obesity — based on a calculation comparing body weight with height — hasn’t changed significantly over the past decade.


It’s tough to explain why abdominal girth keeps increasing while obesity rates remain fairly steady, said study leader Dr. Earl Ford, a medical officer at the federal Centers for Disease Control and Prevention. A growing use of certain medications, like antidepressants, increased sedentary time spent in front of a computer, or a rise in sleep deprivation — all of which are associated with increased belly fat — could explain the trend, he added.

But the gender differences remain a mystery that requires further research to determine whether women have experienced a change in any lifestyle patterns that set them apart from men.

Speaking from my own experience, I’m betting the differences stem from clothing sizes. A man may need to face the truth that his waist is getting bigger when his size 30 slacks no longer button — and he may be more likely to cut his calories or increase his workouts to shed the few pounds he’s gained. A woman, on the other hand, may rationalize that those decade-old pair of jeans that are suddenly too tight must have shrunk in the wash. Her beliefs are confirmed when she’s able to buy a new pair in the same old size — even if it’s actually a few inches bigger in the waist.

Deborah Kotz can be reached at dkotz@globe.com. Follow her on Twitter @debkotz2.