[PHNUTR-L] Study suggests link between obesity, poor bone health

[Kathrynne Holden]

Colleagues, the following is FYI and does not necessarily reflect my own
opinion. I have no further knowledge of the topic. If you do not wish to
receive these posts, set your email filter to filter out any messages
coming from   @nutritionucanlivewith.com    and the program will remove
anything coming from me.
---------------------------------------------------------
Public release date: 26-Nov-2007
http://www.eurekalert.org/pub_releases/2007-11/uog-ssl112607.php

Contact: Sam Fahmy
sfahmy at uga.edu
706-542-5361
University of Georgia

Study suggests link between obesity, poor bone health

Athens, Ga. – Being overweight is a known risk factor for heart disease, 
diabetes and a host of other health conditions. Now, a University of 
Georgia study published in the November issue of the American Journal of 
Clinical Nutrition finds that obesity may also be bad for bone health.

Researchers 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. After adjusting 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.

Previous studies on bone health and obesity used a two-dimensional bone 
densitometer that is commonly used in osteoporosis screenings. Lewis 
explained that a notable shortcoming of the bone densitometer is that it 
does not take into account bone shape and geometry, which have a 
substantial influence on bone strength. The new study used a 
three-dimensional imaging technique that measures both the amount of 
mineral in the bone and its shape and geometry. The study found that, 
surprisingly, 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, lead author of the study, explained 
that muscle exerts force on bones, which stimulates bone growth. 
Overweight people tend to have more muscle surrounding their bones than 
their leaner counterparts, leading 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.”

Lewis said the exact mechanisms by which excess fat hinders bone 
strength are unclear, but studies of obese rats show that they produce 
more fat cells in the bone marrow and fewer bone cells. Since fat and 
bone cells originate from the same precursor, it may be that fat cell 
production is favored over bone cell production in obese people.

The women the researchers studied were 18 and 19, an age at which the 
bones have stopped growing but before age-related degeneration begins. 
Lewis said future studies using three-dimensional bone imaging should 
follow children with normal and high levels of body fat through time to 
see how their skeletons grow. Other researchers have documented 
increased fractures in overweight children, suggesting 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.”
-- 
Kathrynne Holden, MS, RD < fivestar at nutritionucanlivewith.com >
"Ask the Parkinson Dietitian"  http://www.parkinson.org/
"Eat well, stay well with Parkinson's disease"
"Parkinson's disease: Guidelines for Medical Nutrition Therapy"
http://www.nutritionucanlivewith.com/