For people living with obesity, understanding bone health is complicated. Scientists who study bone health are changing how they think about obesity and bone health. Consider this:
- Having a slender build and “small bones” is a risk factor for osteoporosis.
- Losing weight can cause bone loss.
Also, consider this:
- Scientists long believed being overweight could protect us against broken bones.
- People living with obesity have greater bone density.
- Many studies have shown links between greater body weight or body mass index and greater bone density and less risk of fractures1.
Recent studies, however, challenge the belief that being obese protects against broken bones2. Also, other conditions that affect people with obesity, such as Type 2 diabetes and chronic kidney disease, can cause bone loss, poor bone quality and increased risk of fractures.
Understanding how bone health and obesity are related is important for public health. Look at the numbers involved:
- More than 50% of the U.S. population is projected to be obese by 2030.
- About half of U.S. women and a quarter of U.S. men over age 50 will have a fragility fracture in their lifetime.
Studies show obesity poses risks to bone health
The most devastating broken bones due to poor bone health are hip fractures. More than 20% of people die within a year after surgery for a broken hip. Hip fractures also cause lower quality of life and increase risk of death years later3. Being obese puts you at higher risk of dying after a hip fracture. One recent study found that people younger than 75 who were obese and had a hip fracture were more likely to die within 30 days of their injury than people the same age who were normal weight4.
The most common broken bones due to poor bone health are fractures of the bones in the spine. A study from the United Kingdom found that obese men with larger waists had more broken spine bones than underweight or normal-weight men. Even though the men with obesity had greater bone density, they still were at higher risk for fractures. Other factors include whether someone has broken a bone before, their age, smoking, gender, alcohol use, and other diseases and medicines5.
Evidence from recent studies finds that people with obesity might be more likely to break bones on certain parts of their bodies. Ethnicity, gender, and how people carry their weight also affect fracture risk6. A 2022 study that focused on men found that having more lean mass was strongly associated with having higher bone mineral density. Having more fat mass was moderately associated with lower BMD, especially in men with high levels of body fat7.
Obesity affects bone quality
So, are people living with obesity more at risk of breaking bones? Or does being overweight protect against broken bones? The answer is more complicated than one or the other. Heavier people do seem to have greater bone density. But bone density is not the only factor in whether you will break a bone. People living with obesity might have differences in their bone quality that increase their risk of fracture.
What causes these differences in bone quality?
- Obesity might affect how the bones do remodeling.
- Many people with obesity also have Type 2 diabetes, which also increases fracture risk8.
- Chemicals produced by body fat can make the bones less strong9.
- Fat cells and the cells that form bones come from the same stem cells, so more fat cells mean fewer bone-forming cells10.
If you would like to understand your personal risk of bone fractures, you can use a tool called the American Bone Health Fracture Risk Calculator™. The Fracture Risk Calculator is designed for users ages 45 and older. Just answer a few questions about your age, weight, health history, and lifestyle. The Fracture Risk Calculator will give you an estimate of your risk of breaking a bone in the next 10 years. If you are at moderate or high risk, you will get information to help you make a bone health plan.
Find the Fracture Risk Calculator at AmericanBoneHealth.org/calculator.
REFERENCES
1. Gonnelli S, Caffarelli C, Nuti R. Obesity and fracture risk. Clin Cases Miner Bone Metab. 2014;11(1):9-14. doi:10.11138/ccmbm/2014.11.1.009
2. Rafaela Martinez Copes , Fabio Vasconcellos Comim , Juliet Elizabeth Compston , Melissa Orlandin Premaor , Obesity and Fractures in Postmenopausal Women: the Incidence Study in Primary Care, Journal of Clinical Densitometry (2020), doi: https://doi.org/10.1016/j.jocd.2020.01.005
3. Katsoulis M, Benetou V, Karapetyan T, Feskanich D, Grodstein F, Pettersson-Kymmer U, Eriksson S, Wilsgaard T, Jørgensen L, Ahmed LA, Schöttker B, Brenner H, Bellavia A, Wolk A, Kubinova R, Stegeman B, Bobak M, Boffetta P, Trichopoulou A. Excess mortality after hip fracture in elderly persons from Europe and the USA: the CHANCES project. J Intern Med. 2017 Mar;281(3):300-310. doi: 10.1111/joim.12586. Epub 2017 Jan 17. PMID: 28093824.
4. Amin, R., Raad, M., Rao, S. et al. Survival bias may explain the appearance of the obesity paradox in hip fracture patients. Osteoporos Int 32, 2555–2562 (2021). https://doi.org/10.1007/s00198-021-06046-7
5. Luo, J. and Lee, R.Y. (2020), How Does Obesity Influence the Risk of Vertebral Fracture? Findings From the UK Biobank Participants. JBMR Plus, 4: e10358. https://doi.org/10.1002/jbm4.10358
6. Gonnelli S, Caffarelli C, Nuti R. Obesity and fracture risk. Clin Cases Miner Bone Metab. 2014 Jan;11(1):9-14. doi: 10.11138/ccmbm/2014.11.1.009. PMID: 25002873; PMCID: PMC4064448.
7. Jain R, Vokes T, Fat Mass Has Negative Effects on Bone, Especially in Men: A Cross-sectional Analysis of NHANES 2011-2018, The Journal of Clinical Endocrinology & Metabolism, Volume 107, Issue 6, June 2022, Pages e2545–e2552, https://doi.org/10.1210/clinem/dgac040
8. Turcotte AF, O’Connor S, Morin SN, Gibbs JC, Willie BM, et al. (2021) Association between obesity and risk of fracture, bone mineral density and bone quality in adults: A systematic review and meta-analysis. PLOS ONE 16(6): e0252487. https://doi.org/10.1371/journal.pone.0252487
9. Gonnelli S, Caffarelli C, Nuti R. Obesity and fracture risk. Clin Cases Miner Bone Metab. 2014 Jan;11(1):9-14. doi: 10.11138/ccmbm/2014.11.1.009. PMID: 25002873; PMCID: PMC4064448.
10. Chen Q, Shou P, Zheng C, Jiang M, Cao G, Yang Q, Cao J, Xie N, Velletri T, Zhang X, Xu C, Zhang L, Yang H, Hou J, Wang Y & Shi Y. Fate decision of mesenchymal stem cells: adipocytes or osteoblasts? Cell Death & Differentiation 2016, volume 23, pages1128–1139 (published 2/162016)
Posted: 7/28/2022
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