Weight-loss surgery could weaken teens’ bones

By Cara Murez HealthDay Reporter

TUESDAY, June 13, 2023 (HealthDay News) — Weight-loss surgery can have many benefits for obese teens and young adults.

But a new study finds a disturbing side effect. Young people who underwent sleeve gastrectomy, the most common obesity surgery, also had weakened bones.

That doesn’t mean they shouldn’t have surgery, the lead author said doctor Miriam Bredellaprofessor of radiology at Harvard Medical School.

If anything, the research could lay the groundwork for new therapies to target this bone problem, as teens continue to help preserve their bone strength with supplements, healthy eating, and weight-bearing exercises.

Although weaker bones can mean a higher risk of fractures, obesity is linked to diabetes and heart disease, Bredella said.

“Knowing what we know now and in hormone studies, this may represent a target for new therapies that can improve bone health,” Bredella said.

Obesity is a growing problem in the United States, where 22% of 12 to 19 year olds are obese, according to the US Centers for Disease Control and Prevention.

The American Academy of Pediatrics, a leading medical group, recommends that adolescents with severe obesity be evaluated for metabolic or bariatric (weight loss) surgery. Additionally, from age 12, children may be offered weight-loss medication, in addition to recommended lifestyle changes, according to the academy.

Sleeve gastrectomy works by removing between 75% and 80% of the stomach, which limits how much you can eat. The round stomach of the body takes the form of a tube.

It’s becoming increasingly common, with 122,000 surgeries in 2020 compared to 28,000 in 2011, according to the American Society for Metabolic and Bariatric Surgery.

The researchers studied patients aged 13 to 24 who enrolled in the study from 2015 to 2020. Each had moderate to severe obesity with a body mass index (BMI) of 35 or higher.

Of the 54 participants, 25 underwent sleeve gastrectomy and 29 were part of a control group that received advice on diet and exercise. Forty-one participants were women.

Those who had surgery had at least one obesity-related health condition, such as high blood pressure or type 2 diabetes, or a particularly high BMI at age 40 or older.

Each participant underwent a physical exam, blood tests and what is called a quantitative lumbar spine CT scan before their surgery and two years later. This allows quantification of volumetric bone mineral density and determination of bone strength.

It is very accurate at detecting changes in volumetric bone mineral density after extreme weight loss, according to the study.

Bone marrow fat may also be a biomarker of bone quality as it responds to nutritional changes. Patients therefore had proton MRI spectroscopy to quantify bone marrow fat in their lumbar spine.

“These are really sophisticated studies. We do a special type of CT and then we do something called finite element analysis, which is a technique typically used when designing bridges, aircraft or materials,” Bredella said. “It’s really about figuring out how much force is needed for something to break.”

It is such a new technique that there are no normal values ​​for teenagers.

Obese children and adults already have greater bone strength, Bredella explained. This is at least partly because weight has some of the effect of weight-bearing exercise.

Weight loss can take some of that away. In addition, the sleeve gastrectomy removes part of the stomach where hormones good for bone health are made. And, as people eat less, they may also be consuming fewer nutrients.

In the study, researchers found that the control group gained about 1.5 BMI points after two years. During this time, the surgery group lost 11.9 BMI points, on average.

The surgery group had a significant increase in bone marrow fat, but a decrease in bone density and strength, the researchers noted.

Hormones could be a therapeutic target, “or bone marrow fat,” Bredella said. “It may be something that could be targeted for new therapies that have yet to be developed, but at least our study can kind of lay the groundwork for something that can be done in the future.

Even without this, young people who will undergo sleeve gastrectomy could start by eating a healthy diet, exercising, and adding calcium and vitamin D supplements, before and after surgery.

Bredella said she just wants people to know that weight loss surgery can cause bone health to deteriorate.

“That alone is probably our biggest takeaway. That the primary care physician who sees these kids post-surgery is actually looking at their bone health, thinking about nutrition, prescribing vitamin D and calcium, telling kids to doing weight-bearing exercises,” Bredella said.

These young people could also undergo bone scans at an earlier than average age, around 40 or 50 years old.

Dr. Thomas Linkprofessor of radiology at the University of California, San Francisco, called the work extremely valuable.

In childhood and adolescence, people build a reservoir of bones, Link said. This continues until the age of about 25. Then, throughout adulthood, the body begins to empty this reservoir.

“You lose bone mass. You lose bone quality, bone strength. And if you don’t get enough bone, you’re much more likely to get osteoporosis at a later stage,” said Link, co-author of an editorial published with the study.

Fractures in the elderly can be particularly serious. “That’s why you have to be extremely conscientious about these bone issues,” Link said.

Still, like Bredella, Link agreed that surgery for these teens and young adults is still important because of the risks of early death and reduced quality of life with obesity.

“We don’t want these patients not having their surgery, but we want them to take very good care of their bone metabolism,” Link said.

For weight-bearing exercises, that can mean a variety of different activities, from walking to running to various sports, anything that puts weight on the joints, he suggested.

The results of the study were published on June 13 in the journal Radiology.

More information
The US Centers for Disease Control and Prevention has more on childhood obesity.

SOURCES: Miriam Bredella, MD, MBA, professor, radiology, Harvard Medical School and vice chair, faculty affairs and clinical operations, department of radiology, Massachusetts General Hospital, Boston; Thomas Link, MD, PhD, Professor of Radiology and Head, Musculoskeletal Imaging, and Clinical Director, Musculoskeletal and Quantitative Imaging Research Group, University of California, San Francisco; RadiologyJune 13, 2023

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