Obese Teens Have Greater Risk of Developing Multiple Sclerosis

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A study of 238,000 women found that those who were obese at age 18 had twice the risk of developing multiple sclerosis compared to women who were at normal weight as teenagers, according to research published in the journal Neurology.

Researchers from the Harvard School of Public Health used data from nurses taking part in a large study on diet, lifestyle factors and health. Body size was reported by the women using a series of diagrams at the age of 5, 10, and 20. Obesity was defined as having a BMI of 30 or greater. Over the course of the 40-year study 593 women were diagnosed with MS.

Adolescence was found to be the most critical period for determining the link between obesity and MS. Body size during childhood and adulthood was not found to be associated with risk of developing multiple sclerosis.

“Our results suggest that weight during adolescence, rather than childhood or adulthood, is critical in determining the risk of MS. There’s a lot of research supporting the idea that adolescence may be an important time for development of disease, so what we have found is consistent with that. Teaching and practicing obesity prevention from the start – but especially during teenage years – may be an important step in reducing the risk of MS later in life for women,” said Kassandra Munger, ScD, lead author of the study.

Multiple sclerosis is a condition caused by the loss of nerve fibers and their protective myelin sheath in the brain and spinal cord, which causes neurological damage. It is most common among women, with a typical age of onset between 15 and 50.

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Some experts question the results. Susan Kohlhaas, research communications officer for the MS Society, said: "This study does not account for several other factors that may play a role in causing MS. Based on that, more work is needed.”

Obesity in itself is not typically known as a causative factor in the development of multiple sclerosis, but research has found that MS is complicated by the presence of obesity. Because of similar neurological symptoms, such as numbness and fatigue, obesity makes a diagnosis of MS more difficult, delaying the diagnosis and treatment, as reported in the American Journal of Physical and Medical Rehabilitation (February 2009)

The immune system may play a role in the development of MS. Scientists think that certain body cells appear to attack the myelin sheath and cause inflammation. The researchers from the Harvard study feel that obesity contributes to this inflammatory process.

There is also a link between diet and both MS and obesity. Diets high in saturated fats are likely to make MS symptoms worse. The same diet is linked to weight gain.

Also, previous research has found that people with low levels of vitamin D, such as those living farthese from the equator, have an increaed risk of developing MS. Obesity is also associated with low vitamin D levels in the body.

Gary Birnbaum, director of the Multiple Sclerosis Treatment and Research Center near Minneapolis, feels that there probably isn't any single factor that can explain all cases of MS. "If it were that simple we probably would have been able to figure it out by now," he says. "MS may not be a single disease. It may be a syndrome. The pathway may actually be very different for different people."

Denise Reynolds RD LDN

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