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Feature Article

Extra weight: No protection against broken bones, as once thought

Most people, if given a choice, would rather be thin than fat. But some scientists have believed that obesity has at least one redeeming virtue, especially in older people: It may protect against osteoporosis and broken bones. A team of researchers from the New Mexico VA Health Care System, the University of New Mexico, and the Biomedical Institute of New Mexico set out to find out whether that hypothesis is true—and found that it isn't, especially for men.

Osteoporosis is a disorder in which bones become increasingly porous, brittle, and subject to fracture, owing to the loss of calcium and other mineral components. It sometimes results in pain, decreased height, and deformities in the skeleton. It is common in older people, especially women who have gone through menopause. Fractures resulting from osteoporosis often occur in the spine, wrist, and hip, and they can be very dangerous.

"It has been proposed that obesity is protective against osteoporotic fractures," said Lina E. Aguirre, MD, a physician and researcher at the New Mexico VA Health Care System and at the Biomedical Institute. "But data from previous studies have given conflicting results."

Aguirre and her team, under the direction of Dennis Villareal, MD, and Reina Villareal, MD, of the New Mexico VA Health Care System, analyzed data from 133 elderly adults (58 men and 75 women) who were participating in a weight loss and exercise program. The results of their study were presented at the 94 th annual meeting and exposition of the Endocrine Society, which was held in Houston in June 2012, and were published in the meeting's proceedings.i

The team used a technique called dual energy X-ray absorptiometry (DXA) to study body composition and bone mineral density in the study participants. DXA is a specially constructed x-ray machine developed to determine bone mineral content to help detect and treat osteoporosis. The machine also analyzes the fat and lean mass of soft tissue surrounding bones.

The team also calculated HOMA-IR scores for each participant. HOMA-IR is a test that measures insulin resistance, the ability of cells within the body to break down glucose (sugars) in the blood. When the body is less able to break down glucose, it puts out more insulin to stabilize blood glucose levels. Over time, these higher insulin levels can result in a condition called hyperinsulimia, which can make it more difficult for the body to use its stored fat for energy.

In analyzing the data they obtained from the testing, the team divided the study participants into three groups, based on their percentage of body fat. They also divided each group by gender. The men and women in each group had very similar characteristics, except that the women in the study group, on average, had slightly more body fat than men.

They found that males with the highest level of body fat had the lowest levels of bone mineral density among the men, meaning their bones were the weakest. This was true throughout the men's bodies—but, interestingly enough, it was not true in women. Men with high levels of body fat also had the highest levels of insulin resistance. Further analysis of the data determined that higher levels of insulin resistance are a significant predictor of lower levels of bone mineral density.

"Our data suggests that, in the people we studied, obesity did not protect against osteoporosis," says Aguirre. "Men, in particular, are more vulnerable to the adverse impacts of obesity on skeletal health."

VA has long been aware of many of the consequences of obesity on older Veterans' health. These consequences can include heart disease, diabetes, some cancers, sleep apnea, and gallstones. The Department's MOVE program is a weight self-management program for Veterans who want to improve their health. Every VA medical center has a MOVE program coordinator to help Veterans along the road to healthy living and a healthy weight. Veterans who receive their health care from VA and are interested in participating in this program should contact their primary care provider, or visit the MOVE website at www.move.va.gov.



i LE Aguirre, V Kulkarny, S Pascual, CR Qualls, DT Villareal, RC Armamento-Villareal. "Increasing Adiposity Adversely Affects Bone Mineral Density in Elderly Obese Men," Endocr Rev. Vol. 33 (03_MeetingAbstracts): OR18-5.


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