No, you're not just imagining it: Your hips really do get wider as you get older, according to a new study.

Even though most people stop growing in height by the time they hit age 20, researchers have found evidence that the hip bones can keep growing even as people enter their 70s.

"I think it's a fairly common human experience that people find themselves to be wider at the age of 40 or 60 then they were at 20," study researcher Dr. Laurence E. Dahners, a professor in the orthopedics department at the University of North Carolina School of Medicine, said in a statement.

For years, people thought the widening was because of an increase in body fat , but the new findings show that pelvic growth may lead to an increase in waist size as people get older and not just because they put on more weight, Dahners said.

Dahners and his colleagues examined CT scans from 246 people to measure the width and the height of their vertebral body (to determine whether the patients are taller or larger than average to begin with), the width of their pelvic inlet (the middle of the pelvis where, for women, the birth canal opens up) and the distance between the hip joints, as well as the diameter of the hip joints.

There were about 20 males and 20 females in each 10-year age group, starting from people ages 20 to 29 and going up to people ages 70 to 79.

Researchers found that the width of the pelvis, the distance between the hip bones and the diameter of the hip bones all increased as people got older , even after people maxed out height-wise.

The pelvic width of the oldest people in the study (ages 70 to 79) was, on average, about an inch larger than the youngest people (ages 20 to 29), according to the study. That translates to about a three-inch increase in waist size between someone age 20 and someone age 79.

The new study was published May 25 in the Journal of Orthopaedic Research.

Pass it on: People's hips get wider as they get older not just because of fat, but because their pelvic bones actually grow wider.

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