Researchers studied over 10,000 American adults to understand how body shape relates to bone health, specifically looking at the lower spine. They used a new measurement called the Body Roundness Index (BRI) that measures how round your body is, rather than just weight. They found that people with rounder body shapes tend to have weaker bones in their lower spine. This discovery is important because it suggests that the way fat is distributed on your body—not just how much you weigh—might affect bone strength. Understanding this connection could help doctors develop better ways to prevent and treat weak bones as people age.

The Quick Take

  • What they studied: Whether a new way of measuring body shape (called Body Roundness Index) is connected to bone density in the lower spine
  • Who participated: 10,996 adults aged 20 and older from across the United States who participated in a national health survey between 2011 and 2018
  • Key finding: People with rounder body shapes had weaker bones in their lower spine. For every increase in the roundness measurement, bone density decreased slightly. This relationship was strongest at certain body roundness levels.
  • What it means for you: If you have a rounder body shape, you may want to talk to your doctor about bone health and ways to strengthen your bones through exercise and nutrition. However, this study shows a connection, not that one thing causes the other.

The Research Details

This was a large nationwide study using health information already collected from American adults. Researchers looked at data from surveys conducted between 2011 and 2018 that included measurements of body shape and bone density scans of the lower spine. They used special statistical methods to account for other factors that might affect bone health, like age, sex, race, and weight. The researchers also looked for patterns—specifically, whether the relationship between body shape and bone strength was straight or curved (meaning it changed at different body roundness levels).

Previous research showed that the Body Roundness Index (BRI) is better at measuring where fat sits on your body compared to traditional measurements like BMI or waist size. Since where fat is located matters for health, studying BRI’s connection to bone strength could reveal new ways to predict and prevent bone disease. This approach is more precise than just looking at weight alone.

This study used data from a well-respected national health survey that carefully measured both body shape and bone density using standard methods. The large number of participants (nearly 11,000) makes the findings more reliable. The researchers adjusted for many factors that could affect results, making the connection between body shape and bone strength more trustworthy. However, because this was a snapshot in time rather than following people over years, we can’t say that body shape causes weak bones—only that they’re connected.

What the Results Show

The main finding was that people with rounder body shapes had weaker bones in their lower spine. This relationship held true even after researchers accounted for age, sex, race, and other weight measurements. Interestingly, the relationship wasn’t perfectly straight—it changed at a certain body roundness level (7.63). Below this level, the connection was weaker; above it, the connection was stronger. This means that once body roundness reaches a certain point, the effect on bone strength becomes more pronounced. The pattern was similar across most groups of people, regardless of age or race, though it varied somewhat based on traditional weight categories.

When researchers looked at specific groups separately, they found the bone-weakening pattern was strongest in men and in people under 40 years old. The relationship was also clear in non-Hispanic White adults and other racial groups. Interestingly, when looking at people grouped by traditional weight categories (BMI), the pattern was less consistent, suggesting that body roundness might be a better predictor of bone health than standard weight measurements.

Earlier research showed that obesity affects bone metabolism (how your body builds and breaks down bone). This study builds on that by showing that body shape—specifically how round your body is—matters for bone health. The Body Roundness Index appears to be a better tool for predicting bone problems than older measurements like BMI, which only considers height and weight without accounting for where fat is located on your body.

This study shows a connection between body shape and bone strength, but it doesn’t prove that body shape causes weak bones. Because researchers looked at all the data at one point in time rather than following people over years, we can’t determine cause and effect. The study included mostly data from certain time periods, so results might differ in other years. Additionally, the study was based on U.S. adults, so findings might not apply to people in other countries with different genetics or lifestyles.

The Bottom Line

If you have a rounder body shape, consider talking to your doctor about bone health screening, especially as you age. Eating foods rich in calcium and vitamin D, doing weight-bearing exercise (like walking or strength training), and maintaining a healthy weight may help protect your bones. These recommendations are supported by general health evidence, though this specific study suggests body shape is an additional factor to consider. (Moderate confidence level)

This research is most relevant for adults concerned about bone health, people with family histories of weak bones, women approaching or past menopause, and anyone with a rounder body shape. Doctors and health professionals should consider body roundness when assessing bone health risk. People with normal body shapes should still maintain healthy bones through exercise and nutrition, but may have lower risk based on this research.

Changes in bone strength happen slowly over months and years. If you make lifestyle changes based on this research, you wouldn’t expect to see improvements in bone density for at least 6-12 months. Regular check-ups with your doctor can track changes over time.

Want to Apply This Research?

  • Track your waist and hip measurements monthly to monitor body roundness trends, along with weight and exercise minutes. This gives you a complete picture of body composition changes rather than weight alone.
  • Add 30 minutes of weight-bearing exercise (walking, jogging, dancing, or strength training) at least 3 times per week, and log calcium-rich foods daily to support bone health while potentially improving body shape.
  • Create a quarterly check-in to review body measurements, exercise consistency, and nutrition patterns. Set a reminder to discuss bone health screening with your doctor annually, especially if you notice increasing body roundness.

This research shows a connection between body shape and bone density but does not prove cause and effect. These findings are for educational purposes and should not replace professional medical advice. If you have concerns about your bone health, body shape, or risk of osteoporosis, please consult with your healthcare provider. This study was conducted on U.S. adults and may not apply to all populations. Always speak with a doctor before making significant changes to diet or exercise routines, especially if you have existing health conditions.