Introduction <p>Bariatric surgery is approved to promote weight loss and induce remission of obesity-related medical conditions. However, the impact of these procedures on bone density is still debated. This study aimed to assess the effect of bariatric surgeries on bone mineral density using dual-energy X-ray absorptiometry (DXA) scan in sleeve gastrectomy and bypass surgery.</p> Methods <p>The prospective cohort study recruited 32 patients with severe obesity, who underwent metabolic and bariatric surgery. Patients were divided into two groups and monitored for one year. Laparoscopic sleeve gastrectomy group included 18 patients; the Bypass group included 14 patients. The primary outcome was the assessment of bone density by DXA scan. Secondary outcomes included serum calcium, parathyroid hormone, and vitamin D levels.</p> Results <p>Patients who underwent gastric bypass surgery had a higher incidence of bone loss at the femoral neck (<i>p</i> = 0.030) and radius (<i>p</i> = 0.043) compared to those who underwent sleeve gastrectomy. In the sleeve gastrectomy group, bone density at the spine was significantly reduced at one year postoperatively, while no statistically significant change was observed in the gastric bypass group. Vitamin D level was significantly higher in the sleeve gastrectomy group than in the bypass group (<i>p</i> = 0.029). Patients compliant with medications demonstrated significantly less bone loss with higher calcium and vitamin D and lower parathyroid hormone levels compared to noncompliant patients (<i>p</i> &lt; 0.05).</p> Conclusion <p>Metabolic and bariatric surgery is associated with changes in bone mineral density, most notably after gastric bypass procedures, accompanied by reductions in calcium and vitamin D levels and increased parathyroid hormone. These findings underscore the importance of early postoperative monitoring of bone health using DXA and biochemical markers, particularly after bypass procedures and in patients with poor adherence to supplementation.</p>