Popular weight-loss surgeries in teens weaken bones

“Childhood obesity is a major public health problem that has been increasing over the past 10 years,” said lead investigator Miriam A. Bredella, MD, professor of radiology at Harvard Medical School in Boston, Massachusetts, and vice chair of the radiology department at Massachusetts General Hospital in Boston. “Sleeve gastrectomy is the most common bariatric surgery performed in children and adults.”

Sleeve gastrectomy removes approximately 75% of the stomach to limit food intake and induce weight loss. It results in a typically rounded stomach that takes the shape of a tube or sleeve. The number of sleeve gastrectomy procedures in adolescents increased by a factor of 100 between 2005 and 2014.

“In adults, bariatric surgery can have long-term effects on bone, leading to a higher risk of fractures,” said Dr. Bredella. “We wanted to determine the effects of sleeve gastrectomy in adolescents during the critical years of bone mass building.”

The study examined 52 adolescents with moderate to severe obesity, 26 of whom underwent sleeve gastrectomy. The remaining 26 were in the control group. The mean age was 17.5 years and the mean body mass index (BMI) was 45. BMI of 30 or above is considered obese. Thirty-eight of the study participants were girls. Before and 12 months after sleeve gastrectomy (or no surgery), patients underwent quantitative lumbar spine CT to quantify volumetric bone mineral density. Quantitative CT is a highly accurate technique for detecting changes in volumetric bone mineral density after extreme weight loss.

Recent studies have shown that bone marrow fat responds to dietary changes and can serve as a biomarker for bone quality. Therefore, patients underwent proton MR spectroscopy to quantify bone marrow fat of the lumbar spine.

One year after surgery, the adolescents who underwent a sleeve gastrectomy lost 34 (+/- 13) kg, or 75 (+/- 28) pounds, while there was no significant change in weight in the control group. Compared to controls, sleeve gastrectomy patients had a significant increase in bone marrow fat and a decrease in bone density in the lumbar spine.

“Adolescents who underwent sleeve gastrectomy had bone loss and an increase in bone marrow fat, despite marked body fat loss,” said Dr. Bredella. “While weight-loss surgery is successful for weight loss and improving metabolic disorders, it has negative effects on bone.”

Dr. Bredella said the loss of bone density after a sleeve gastrectomy was expected because a greater weight load strengthens the bones. In addition to a loss of bone density, other effects of weight loss surgery include a disruption of hormones and nutrients important for bone health.

“We need to identify mechanisms that help prevent bone loss in these patients and make obese adolescents more aware of bone health,” she said. “Adolescence is the critical time for bone mass building, and any process that interferes with bone building during this time can have serious consequences later in life.”

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Co-authors are Vibha Singhal, MD, Nazanin Hazhir Karzar, MD, Abisayo Animashaun, BS, Amita Bose, BS, and Madhusmita Misra, MD, MPH

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