The association between body mass index and osteoporosis, with consideration of sex differences: a systematic review and dose-response meta-analysis

Abstract This meta-analysis reveals a significant association between Body Mass Index (BMI) and the risk of osteoporosis. Being underweight may increase the risk of osteoporosis, while being overweight or obese may reduce the risk of osteoporosis. Specifically, each 1-unit increase in BMI is associated with a 9% reduction in osteoporosis risk, emphasizing its importance in bone health assessment. Objective This meta-analysis evaluated osteoporosis risk across BMI categories and explored the BMI-osteoporosis dose-response relationship. Methods We systematically searched the Web of Science, Cochrane Library, Embase, and PubMed databases from their inception to September 2025. Following independent literature screening, data extraction, and quality assessment by two researchers, we conducted meta-analyses using RevMan 5.4.0 software, with dose-response relationships analyzed through generalized least squares trend estimation (GLST) and restricted cubic spline functions. Results The meta-analysis incorporated 39 studies involving 94,453 patients. Pooled results demonstrated that underweight patients faced a 3.05-fold increased osteoporosis risk (OR=3.05, 95%CI:2.74–3.40, P<0.05), with gender stratification revealing higher vulnerability in men (OR=3.58, 95%CI:2.99–4.98) versus women (OR=3.12, 95%CI:2.58–3.77). Conversely, overweight patients have a lower risk of osteoporosis (OR=0.50, 95%CI:0.42–0.58), consistently observed in both genders (men: OR=0.36, 95%CI:0.26–0.49; women: OR=0.54, 95%CI:0.46–0.65). Obesity further reduced risk (OR=0.36, 95%CI:0.29–0.44), though male-specific data lacked significance (OR=0.44, 95%CI:0.11–1.83, P>0.05) compared to women (OR=0.37, 95%CI:0.30–0.46). Dose-response analysis indicated a 9% risk reduction per 1-unit BMI increase (OR=0.910, 95%CI:0.888–0.932). Conclusions This meta-analysis revealed a significant association between BMI and osteoporosis risk. Underweight individuals exhibited a markedly elevated risk of osteoporosis, whereas overweight and obesity appeared to be protective factors. Based on our dose–response analysis of nine studies, each 1-unit increase in BMI was associated with a 9% reduction in osteoporosis risk. However, the higher BMI warrant careful clinical consideration. We recommend identifying underweight populations as high-risk groups for osteoporosis and developing gender-specific preventive strategies.