Osteoporosis Risk Increases as BMI Decreases Into Adulthood

A lower body mass index (BMI) during adolescence was linked to a greater risk of osteoporosis in adulthood, highlighting a direct inverse association between osteoporosis and patient weight, according to results of a study published in JAMA Network Open.¹ 

“Evidence for the negative effect of low BMI on different bone health parameters, including bone mineral density, fracture risk, and risk for osteoporosis, are abundant,” wrote authors of the study. “However, evidence regarding the effect of BMI at a young age on bone health in later life is insufficient, and existing studies lack data regarding comorbid conditions with a potential effect on bone health.”

Osteoporosis is a debilitating disease that impacts patients’ bone health, leading to a decrease in bone mass, structure, and strength. In turn, patients often experience an increased risk of fractures. According to the National Institute of Arthritis and Musculoskeletal and Skin Diseases, osteoporosis is often referred to as a silent disease with minimal perceived symptoms. Many patients will not be aware of their diagnosis until they break a bone.²

READ MORE: Extremely Severe Pediatric Obesity Prevalence Increased Over Last 15 Years

The increase in patients’ BMI usually translates to greater health risks, such as type 2 diabetes, stroke, liver disease, and many other potential complications.³ In the case of osteoporosis, however, previous evidence has highlighted that the disease is more prominent among patients with lower rather than higher BMIs, those who are overweight, and obese individuals.

Some studies have explored the optimal BMI for minimizing osteoporosis risk, which is around 23 to 24.9 kg/m,^2,4 and the association between low BMI and bone fractures.⁵ However, few have explored how changes in BMI from adolescence into adulthood affect osteoporosis risk.

“The goal of this research is to examine the association between BMI [in] adolescence, adolescent-adult BMI trajectory, and the risk of osteoporosis in adulthood,” wrote the authors.¹

They conducted a retrospective study spanning data from 1967 to 2019. All participants were born in Israel and aged between 16 and 19 years. The researchers gathered participants’ weight and height at baseline to determine their BMI at adolescence. The main outcome sought was an osteoporosis diagnosis from the beginning of the study until 2022.

The final analysis included 1,083,491 patients aged 16 to 19 years. Among the study participants, 4.58% of women and 1.13% of men received osteoporosis diagnoses during the 50-plus-year period. Regarding the BMI characteristics of the entire population, a majority of participants were either between the 10th and 49th percentiles (40.3%) or the 50th and 80th percentiles (32.95%). Just 4.91% were located in the lowest BMI group under the third percentile, and 5.12% were in the highest BMI group above the 95th percentile.

“We report an adjusted [HR] of 1.88 and 1.82 among underweight women and men, respectively, that monotonically decreased to 0.86 and 1.14 for those with obesity,” they continued.¹ “Furthermore, a history of being underweight in adolescence nearly doubled the risk for osteoporosis in both sexes, regardless of weight status in early adulthood.”

Historical results of Israeli adolescents and their osteoporosis risk in adulthood were significantly in line with previous research findings. As BMI decreased into adulthood, patients saw a spike in osteoporosis risk, highlighting continued notions of keeping optimal BMI levels above those of individuals who are significantly underweight.

Multiple studies have now supported the link between osteoporosis and low BMI. Patients and providers should focus on the optimal BMI levels that will translate to improved outcomes. With the additional health risks often accompanied by high BMI, providers will not be inclined to promote a high BMI to reduce osteoporosis risks. Instead, providers should focus on ideal BMI levels between the rates denoting underweight and obesity.

“In this cohort study of 1,083,491 adolescents, we provided evidence for an association between BMI in adolescence and the risk of osteoporosis in adulthood, along with the associations of weight changes,” concluded the authors.¹ “This emphasizes the importance of healthy weight in adolescence for the prevention of osteoporosis, among other diseases later in life.”

READ MORE: Obesity Management Resource Center

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References

1. Simchoni M, Landau R, Derazne E, et al. Adolescent body mass index, weight trajectories to adulthood, and osteoporosis risk. JAMA Netw Open. 2025;8(8):e2525079. doi:10.1001/jamanetworkopen.2025.25079

2. Osteoporosis. National Institute of Arthritis and Musculoskeletal and Skin Diseases. Updated December 2022. Accessed August 19, 2025. https://www.niams.nih.gov/health-topics/osteoporosis

3. Health risks of overweight & obesity. National Institute of Diabetes and Digestive and Kidney Diseases. Updated May 2023. Accessed August 19, 2025. https://www.niddk.nih.gov/health-information/weight-management/adult-overweight-obesity/health-risks

4. Lee JH, Kim JH, Hong AR, et al. Optimal body mass index for minimizing the risk for osteoporosis and type 2 diabetes. Korean J Intern Med. 2020;35(6):1432-1442. doi:10.3904/kjim.2018.223

5. Park SM, Park J, Han S, et al. Underweight and risk of fractures in adults over 40 years using the nationwide claims database. Sci Rep. 2023;13(1):8013. doi:10.1038/s41598-023-34828-y