- This prospective study investigated the two-year effects of sleeve gastrectomy on bone health in 54 adolescents and young adults with obesity, comparing surgical participants with controls who received only counseling about diet and exercise
- As assessed with quantitative CT, bone strength, trabecular bone mineral density (BMD), integral BMD, cortical BMD, and bending stiffness decreased significantly in the surgical group
- The greatest decreases in bone biomechanical properties occurred in participants with the largest reductions in body mass index and those who lost the most abdominal fat and muscle
- The effects of metabolic/bariatric surgery on bone health need to be emphasized to clinicians, especially those in primary care, so patients can receive proper follow-up care throughout their lifetimes
- The control group did not show the increases in bone strength and BMD that are typical of adolescents, which implies obesity itself has negative effects on bone in this age group
Sleeve gastrectomy (SG) and other types of metabolic/bariatric surgery (MBS) are being performed increasingly often in adolescents and young adults, thanks to their effectiveness in the five-year Teen-LABS study published in NEJM. However, MBS is known to cause reductions in bone mineral density (BMD) in adults as well as pediatric patients.
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Adding to the caveats, researchers at Massachusetts General Hospital recently reported in Radiology that sleeve gastrectomy in adolescents and young adults was associated with reduced vertebral bone strength and density as measured with biomechanical CT and increased bone marrow adipose tissue (BMAT) as measured with proton MR spectroscopy.
The team conducted a prospective longitudinal study of 54 patients ages 13 to 24 enrolled between 2015 and 2020. Two nonrandomized groups were defined:
- SG group—25 patients (80% female; mean age 18) who underwent sleeve gastrectomy because of at least one obesity-related comorbidity or body mass index ≥40 kg/m2
- Control group—29 patients (72% female; mean age 18) who received dietary and exercise counseling and did not intend to undergo SG
All participants were advised to take supplemental vitamin D throughout the study.
Inclusion required a biomechanical CT study at baseline and 24 months after surgery. At baseline and 24 months, most patients also underwent proton MR spectroscopy of the lumbar spine. All imaging and analyses were performed blinded to the group assignment.
At 24 months after surgery, the average change in BMI was:
- SG group: −12 kg/m2 (P<0.001 vs. baseline)
- Control group: +1.5 kg/m2 (P=0.02 vs. baseline; between-group difference, P<0.001)
Biomechanical CT Changes
From baseline to the 24-month visit, there were:
- SG group: Significant decreases in bone strength, trabecular BMD, integral BMD, cortical BMD, and bending stiffness
- Control group: Non-significant decreases in all metrics except bending stiffness, in which there was a minor but statistically significant increase
Between-group changes remained significant after adjustment for baseline BMI, but except for bending stiffness, they lost significance after controlling for 24-month change in BMI. That suggests the reductions in bone parameters were driven principally by weight loss.
Increases in trabecular and cortical bone parameters and strength are expected in adolescence, a critical time for bone accrual. The absence of these changes in the control group implies obesity itself has negative effects on bone in adolescents.
Biomechanical CT Changes and BMAT Changes
Changes in vertebral strength, bending stiffness, and integral and trabecular BMD:
- Correlated positively with changes in BMI, muscle, and visceral and abdominal subcutaneous adipose tissue (r = 0.34 to 0.65; P = 0.02 to <0.001)
- Correlated inversely with vertebral BMAT (r = −0.33 to −0.47; P = 0.001 to 0.03)
Clinician Awareness Needed
As MBS continues to become more frequent in adolescents, its effect on bone health needs to be emphasized to clinicians, especially those in primary care. After MBS, patients need optimal dietary supplementation with vitamin D and calcium, monitoring of bone mass, and initiation of appropriate therapy when necessary.
The effects of MBS on BMAT might represent a target for future therapies.
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