Common Weight-Loss Surgery Weakens Bones in Obese Adolescents

By Megan Brooks

December 01, 2020

NEW YORK (Reuters Health) - Obese children who undergo sleeve gastrectomy experience a reduction in bone mineral density and an increase in fat within bones of the lumbar spine, according to a new study.

"Adolescence is the time when we build up our bone mass so anything that interferes with this process might have dire consequences later in life," Dr. Miriam Bredella of Harvard Medical School told Reuters Health by email.

"While weight loss surgery is helpful to lose weight and reduce risk of cardiometabolic disease, one needs to make sure to optimize bone health before and after undergoing such surgery," added Dr. Bredella, who is vice chair of the radiology department at Massachusetts General Hospital.

It will also be important to find new ways to treat bone loss in children who undergo weight loss surgery, Dr. Bredella said in presenting her findings at the Radiological Society of North America (RSNA) annual meeting.

"With the ongoing obesity epidemic, more and more children undergo weight loss surgery. We know from studies in adults that weight loss surgery is bad for bones but no studies have examined detailed effects of weight loss surgery on bones in adolescents," she told Reuters Health.

The study included 52 adolescents (mean age 17.5 years; 38 girls) with moderate-to-severe obesity (mean BMI, 45). Half underwent sleeve gastrectomy and did not. Before and 12 months after sleeve gastrectomy (or no surgery), the patients underwent quantitative CT of the lumbar spine, to quantify volumetric bone mineral density and proton MR spectroscopy to quantify bone marrow fat of the lumbar spine.

"This is the first study that uses quantitative CT (which is less susceptible to changes in body weight) to assess volumetric bone mineral density and the first study that examines fat within bones (bone marrow adipose tissue) before and after weight loss surgery in adolescents," Dr. Bredella told Reuters Health.

At one year, adolescents who underwent sleeve gastrectomy lost 34 (+/-13) kg, while there was no significant change in weight in the control group.

Compared to the no-surgery controls, teens who underwent sleeve gastrectomy showed a decrease in volumetric bone mineral density in the lumbar spine and an increase in lumbar bone marrow adipose tissue.

Dr. Bredella provided the following two examples in her presentation. In a 17-year-old female, volumetric BMD was 183 mg/cm3 before surgery and had decreased to 146 mg/cm3 at one year. In an 18-year-old female, marrow fat before surgery was 0.20 lipid to water ratio and increased to 0.41 at 12 months.

"While weight loss surgery is successful for weight loss and improving metabolic disorders, it has negative effects on bone," Dr. Bredella said in a statement from RSNA. "We need to identify mechanisms that will help prevent bone loss in these patients and to make adolescents with obesity more aware of bone health."

The study was funded by the National Institutes of Health. The authors have indicated no relevant disclosures.

SOURCE: RSNA 2020, presented November 29, 2020.