Teenage Bone Density Declines Following
Sleeve Gastrectomy

Ingrid Hein

December 03, 2020

Adolescents who undergo sleeve gastrectomy have lower bone density and higher bone marrow fat at 1 year following surgery, new research shows.

Dr Miriam Bredella

"It's almost paradoxical," Miriam Bredella, MD, of Massachusetts General Hospital in Boston, told Medscape Medical News. "Despite marked loss of body fat, these children have more fat in their bones and decreased bone density."

She explained that the dissected part of the stomach is filled with anabolic cells that are important for building bone mass. "When those cells are cut out, the body cannot produce the hormones for building up bone." It's a malabsorption problem, she added. "Cutting out parts of the stomach or gut leads to less absorption."

It is well known that bariatric surgery in adults has long-term effects on bone, she said, but this is the first time it has been studied in children.

"Nobody thinks about bone loss in children, but it's extremely important," Bredella reports. "The adolescent years up to age 25 are when we accrue bone density, so if something happens during this critical time, it can lead to weak bones later in life." In the case of these adolescents, peak bone mass is never reached.

To investigate the effects of sleeve gastrectomy on bone density and marrow adipose tissue in extremely obese teenagers, researchers at Massachusetts General Hospital and Harvard Medical School recruited 52 adolescents with a mean body mass index (BMI) of 45. They measured volumetric bone mineral density using quantitative computer tomography (QCT) of the lumbar spine.

"We used QCT instead of DEXA [dual energy x-ray absorptiometry] scan because it isn't affected by changes in soft tissue; it's less susceptible to extreme changes in body weight," Bredella said. "With DEXA scan there are too many artifacts."

Half of the group (n = 26) underwent surgery. At 1 year, those who underwent surgery lost an average of 34 kg (75 lb). Adolescents in the control group lost an average of 0.2 kg (0.5 lb) (P < .0001).

Both groups repeated the QCT scan at the 1-year follow-up. Researchers found a decrease in bone density in those who underwent sleeve gastrectomy vs. controls (P = .046).

In her presentation, Bredella showed the QCT of the L2 spine in a 17-year old female before surgery and 12 months later. Her volumetric bone mineral density decreased from 183 mg/cm3 to 146 mg/cm3.

"Sleeve gastrectomy in children is bad for bones," Bradella said. "You have to take care of your bones. This is something people are not thinking about and it probably won't be a problem when they're young but will likely affect these patients with osteoporosis when they are older."

Patients need to be aware of this, she warns, and take steps to combat the bone loss. "Drinking milk, taking vitamin D, and doing weight-bearing exercise may help increase the bone density," she said

The increased fat in the bone is also concerning, she said. "Increased fat in the bone is a phenomenon that we see in anorexic patients," Bredella explained.

The body appears to store the fat in bone in case of need later on, she explained. "We know that in severe states of malnutrition the body has the ability to metabolize the fat in the bones."

The obesity epidemic in America has given way to a 100-fold increase in sleeve gastrectomy procedures in teenagers between 2005 and 2014. "These patients need this surgery so they don't die of cardiac arrest or diabetes," she said. "But we need to make sure they get their bone mineral density checked frequently."

"The results of this study are important," Marc Michalsky, MD, Nationwide Children's Hospital, Columbus, Ohio, told Medscape Medical News. "But they need to be put into context."

"There is an impetus and argument to support bariatric surgery as it offers a significant reduction in BMI and an associated reversal and complete amelioration of obesity related diseases."

What this study doesn't address, he said, is whether this population will experience an increase in bone density-related fractures down the road.

"These results are a snapshot in time — a picture of one postoperative time point," Michalsky pointed out. "Are we seeing a process that represents continued change in bone mineralization? It's not unreasonable to assume that the radiological findings here may lead to real clinical impact, but we don't know."

Bredella and Michalsky have disclosed no relevant financial relationships.

Radiological Society of North America (RSNA) Annual Meeting:
Abstract PD-1A-48 Effect of Sleeve Gastrectomy on Marrow Adipose Tissue in Adolescents with Obesity. November 29-December 4, 2020.

Ingrid Hein is a freelance health and technology reporter based in Hudson, Quebec.

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