Muscles, not fat, strengthen bones

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NEW YORK, Feb 2 (Reuters) Researchers speculated that excess fat, which places more weight on the bones, may help build stronger bones in young people. However, a new study has found that this is not the case.

To investigate the accuracy of this ''traditional paradigm,'' Dr Vicente Gilsanz and colleagues from Children's Hospital Los Angeles and colleagues used a technique called dual X-ray absorptiometry and CT scanning to precisely measure body fat, lean body mass, bone density and mineral content in 300 people between 13 and 21 years of age. Half were female and half were male.

The researchers found strong associations between lean body mass and bone size and density. But the amount of fat mass either had no relationship to measures of bone strength or a negative one, meaning the more fat mass, the less dense the bone.

The findings back up the idea that ''bone strength is primarily determined by dynamic loads from muscle force, not static loads, such as fat mass,'' Gilsanz and his colleagues write in the Journal of Clinical Endocrinology & Metabolism. Fat may also secrete substances that affect bone metabolism, they add.

The researchers conclude that the findings ''provide compelling evidence that despite increased mechanical loading, adipose tissue is not beneficial to bone structure in young men and women.''