Surgery May Lead
to Weakened Bones
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
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
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