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article imageStudy Uncovers Link Between Poor Bone Health and Obesity

By Bob Ewing     Nov 27, 2007 in Health
Being overweight is a known risk factor for heart disease, diabetes and a host of other health conditions. a University of Georgia study just published finds that obesity may also be bad for bone health.
If you are obese you increase the likelihood that you will develop heart disease, diabetes and many other health conditions. This is not new information. What is new is a study just published in the November issue of the American Journal of Clinical Nutrition.
The study was conducted by a research team from the University of Georgia and according to an University press release, the study found obesity may also be bad for bone health.
The team conducted a series of conducted advanced three-dimensional bone scans on 115 women ages 18 and 19 with normal (less than 32 percent) and high (greater than 32 percent) body fat.
When they adjusted for differences in muscle mass surrounding the bone, the researchers found that the bones of participants with high body fat were 8 to 9 percent weaker than those of normal body fat participants.
“Obesity is an epidemic in this country, and I think this study is critical because it highlights another potential negative health effect that people haven’t considered,” said study co-author Richard D. Lewis, professor of foods and nutrition at the UGA College of Family and Consumer Sciences.
Up until this study, research on bone health and obesity used a two-dimensional bone densitometer that is commonly used in osteoporosis screenings.
According to Lewis, there is a notable shortcoming in using the bone densitometer, which is, it does not take into account bone shape and geometry, which have a substantial influence on bone strength.
The three-dimensional imaging technique measured both the amount of mineral in the bone and its shape and geometry. It was found that, much to the researchers’ surprise, normal- and high body-fat young adult females have comparable bone strength in a direct comparison that does not account for muscle mass.
“The fact that the two groups had similar bone strength measures is remarkable in itself, because you would expect it to be higher in the heavier person,” Lewis said.
Doctoral candidate Norman Pollock who was the lead of the study, explained that muscle exerts force on bones, which stimulates bone growth. People who are overweight tend to have more muscle surrounding their bones than their leaner counterparts; this has lead most researchers to assume that being overweight is good for bone health.
“When we corrected for the amount of muscle, we found that the obese person is not making as much bone as they should be for the amount of muscle that they have,” Pollock said. “People haven’t observed that in the past because they weren’t using the three-dimensional scan.”
The exact mechanisms by which excess fat hinders bone strength remain unclear; however, studies of obese rats show that they produce more fat cells in the bone marrow and fewer bone cells.
Both fat and bone cells originate from the same precursor, so it is possible that fat cell production is favoured over bone cell production in obese people.
The researcher studied women who were 18 and 19 years old, an age at which the bones have stopped growing but before age-related degeneration begins.
Future studies could use three-dimensional bone imaging to follow children with normal and high levels of body fat through time to see how their skeletons grow.
Increased fractures in overweight children have been have documented by researchers; this suggests that childhood obesity may be particularly detrimental to bone health.
“When you’re young you have the capacity to change the shape of your bones, but when you get older you don’t have that capacity.” Lewis said. “And because of that, childhood obesity could have a significant, long lasting negative impact on the skeleton.”
More about Obesity, Bone, Health
 
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