A recent paper showed a 2 fold increase to develop MS if the person was obese as a teenager. Another medical condition associated with obesity is Pseudotumor Cerebri which is a condition where the intracranial pressure increases. Incidentally the initial damage is done to the optic nerve if not treated.
I came across a paper published in 2007 to understand the reason
"Conclusions.: These data support the hypothesis that central obesity raises intra-abdominal pressure, which increases pleural pressure and cardiac filling pressure, which impede venous return from the brain, leading to increased intracranial venous pressure and increased intracranial pressure associated with pseudotumor cerebri."
Now this might as well be applied to CCSVI.
I cannot find an explanation if MS was just an autoimmune disorder.
http://www.neurology.org/cgi/content/abstract/49/2/507
http://www.medpagetoday.com/Neurology/M ... osis/16922