Obesity rates continue to rise, and more and more people are seeking and even being encouraged by their doctors to undergo surgery to reduce their weight. The potential benefits are widely recognized—the risk of diabetes, premature death, heart attack and stroke associated with obesity are all greatly decreased. But there is also a potential for some less desirable outcomes which may not be fully understood.
Concern is coming to focus in particular on the possible damage to bone strength and structure following bariatric surgery.
Fractures increase following bariatric surgery: The Mayo Clinic Study
Bariatric surgery doubled the risk of fracture among patients whose records were studied by a team of Mayo Clinic researchers. Their findings were reported by Jackie Clowes, M.D., Ph.D., of the Mayo Clinic in Rochester, Minn., at the June 2009 Endocrine Society meeting.
The scientists had suspected they would find some increased susceptibility due to previously documented increases in the rate of bone turnover following bariatric surgery. The degree of the increase took them by surprise, however. Noted Clowes, “The established opinion is that obesity protects against osteoporosis and, therefore, fractures.”
The Mayo study involves an ongoing review of 292 cases of medically obese patients who underwent bariatric surgery at Mayo between 1985 and 2004. 97 records have been analyzed to date. Most are female, and most experienced standard gastric bypass surgery.
Following their surgery, 21 of the patients whose cases were reviewed had experienced some kind of fracture, and some had multiple incidents, for a total of 31 individual fractures. While fractures occurred in many locations throughout the body, breaks happened most frequently in the hands and feet—the rate of incidence there was three to four times greater than predicted.
The research team is continuing to review the records of the remaining cases. Their report will be published in The Journal of Clinical Endocrinology & Metabolism.
Calcium and bone deficiencies after weight loss surgery: The Columbia Study
The Mayo findings reinforce concerns raised by an earlier study about bone loss following weight loss surgery. Researchers from Columbia University College of Physicians & Surgeons in New York City studied the cases of 23 obese patients who had chosen to undergo gastric bypass procedures.
Extensive tests and analyses were made of patients’ bone mineral density, serum calcium, vitamin D and parathyroid hormone levels prior to their surgeries and afterward, at 3-month intervals for a year.
Within the year after the surgery, while patients had succeeded in losing almost 100 pounds on average, they also experienced measurable decreases in their bone mineral density at the hip and the femur—prime danger areas for fracture. They also showed deficiencies in calcium and vitamin D levels probably due to the inability of the rerouted digestive tract to absorb these nutrients through the stomach and upper intestine.
“We found that those who lost the most weight also lost the most bone,” notes Dr. Shonni Silverberg, co-author of the Columbia study.
“The calcium and vitamin D deficiencies…may be restored if the amount of calcium and vitamin D supplementation is increased appropriately” added Silverberg.
Together the Mayo and Columbia research findings emphasize the need for continuing assessment of bone strength and calcium and vitamin D levels in patients who have had bypass surgery and resultant significant weight loss.
To read the Columbia study, “The Decline in Hip Bone Density after Gastric Bypass Surgery Is Associated with Extent of Weight Loss,” by J. Fleischer, E. M. Stein, M. Bessler, M. Della Badia, N. Restuccia, L. Olivero-Rivera, D. J. McMahon and S. J. Silverberg”, see The Journal of Clinical Endocrinology & Metabolism,Vol. 93, No. 10 3735-3740.
For more information on the Mayo study, see