Talk about big boned! The 30-yard-long sculpture “Calamita Cosmica” (“Cosmic Magnet”) by Italian artist Gino De Dominicis is anatomically to scale, with the exception of the unusually long nose. (Photo by Topic Photo Agency/Corbis)

During my chunky phase as a pre-teen, a family member once comforted me by telling me I was just “big boned.” I was too young to understand what she was insinuating — this was before Eric Cartman’s catchphrase “I’m not fat, I’m just big boned” was a thing — but at the time, I believed her.

And I’ve always had a sneaking suspicion she might be right.

My entire adult life, I’ve been about 10 to 20 pounds heavier than I look. Even at ages where people didn’t say a lower number just to be polite, outside observers would always guess that my weight was at least 10 pounds less than it actually was. Close friends I mentioned this to would agree that my frame and size never quite seemed to match the number on the scale. My body is JC Penney-catalog average: not particularly stocky, tall, muscular, or possessing any other feature that would explain the idea that I simply seemed to be denser than other people.

Now, research is beginning to conclude what surgeons and scientists have observed for years: Some people really do have bigger and heavier bones than others. Through advances in technology that have made accurate body composition testing more convenient and affordable, experts are now able to gather and analyze large amounts of data in ways they weren’t able to before.

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A recent study examined the body composition of more than 26,000 adults. The subjects had undergone dual-energy X-ray absorptiometry (DEXA) scanning, which uses X rays to measure body fat, lean tissue, and bone mass. (You may recognize the scans from The Biggest Loser, which featured them prominently.)

Tall people have disproportionately larger bones compared with shorter people, the research discovered. “In taller individuals, the bones have to support a greater load, so a larger percentage of a tall person’s weight is actually in their skeleton,” said study coauthor Steven B. Heymsfield, MD, of Louisiana State University’s Pennington Biomedical Research Center.

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(Illustration by Viaframe/Corbis)

To maintain strength, the width of the bone has to increase more than its length, which is why tall bones are disproportionately bigger, Heymsfield explained. “It’s the same thing with a building,” he told Yahoo Health. “When you build a tall building, you just can’t keep all the proportions the same. You have to build a larger foundation and an entirely different structure.”

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There is also a big difference in bone size from one person to another, said Steven Gausewitz, MD, chief of staff at Hoag Orthopedic Institute in Irvine, California. “I do surgery on the skeleton all the time, and when we do hip and knee replacements, we need to have a really big variation of sizes of prosthetics,” he said. “You have people with wide bones and people with small, skinny bones, and sometimes it’s not proportional to your size.”

The size of your frame — the width of your shoulders, the circumference of your wrist — is mostly genetic. But there are a number of lifestyle factors that can influence bone thickness and density. For example, people who gain a lot of muscle or body fat tend to develop stronger bones, Gausewitz explained, because the bone changes in response to the stress of carrying extra weight. Bones become stronger by increasing the width of their outer protective layer, the cortex, which also makes the bone heavier.

The bottom line: “Some people really do have heavier bones,” Heymsfield said. Let’s just all agree not to share this news with Eric Cartman, OK?

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