Obesity Surgery May Lead
to Weakened Bones
Excerpt By Jacqueline Stenson, Reuters Health

People who have undergone gastric bypass surgery to lose large amounts of weight may also lose bone mass, even if they're taking recommended calcium supplements to help keep their bones strong, new findings suggest.

A study that followed patients for about 10 months after the surgery found they were losing more bone than they were replacing. Bone is a dynamic tissue that is constantly being created and destroyed by two types of cells, which will maintain bone strength if the cells are in balance.

It's not clear if the increase in bone turnover seen in obese patients is a lasting effect that could put patients at risk for significant bone loss leading to osteoporosis, but the results raise concerns, said study author Dr. Penelope Coates, an endocrinologist at the University of Pittsburgh in Pennsylvania.

The reason why it is occurring is also unclear, said Coates.

One potential explanation is that the surgery, which by design reduces the absorption of calories, also decreases calcium absorption. Another possibility, she said, is that the excess body weight that once put "increased mechanical force" on these patients' bones -- causing them to become stronger, just as weight-lifting helps build bone -- has decreased, so the bones are simply adjusting to the reduced weight burden.

Whatever the reason, patients should have their bone density measured every couple of years, Coates said here Sunday at the annual Experimental Biology meeting.

If bone loss is detected, patients may need more than the 1,000 milligrams of supplemental calcium that is currently recommended for them, she said.

The new study involved 27 male and female patients who had the popular Roux-en-Y gastric bypass surgery and another 29 people who were awaiting the procedure. During the surgery, doctors staple off a section at the top of the stomach to form a small pouch that can hold only a small amount of food. They also add a bypass that allows food to circumvent part of the small intestine, limiting the absorption of calories.

Ten months after surgery, patients had lost an average of 80 to 100 pounds. At the same time, urine and blood tests indicated that bone was breaking down faster than it was being rebuilt.

"The more weight people lost, the higher their rate of bone breakdown," Coates said.

By comparison, in patients awaiting surgery, bone was breaking down and rebuilding at similar rates, as it should.

"The major finding is that the rate of bone breakdown was higher -- about twice as high -- among those who had surgery as those who didn't," Coates said.

Nonetheless, bone scans did not reveal that surgical patients were showing clear evidence of bone loss, said Coates, possibly because it was too soon to see such an effect.

She and her colleagues plan to continue studying patients to see if the early signs of bone turnover actually translate into marked bone loss over time.

Reference Source 89

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