What could cause a high sed rate? my sed rate is 56, doctor doesnt know why. i am overweight. does this indicate something serious?

An elevated sed rate is a nondiagnostic finding. It signifies increased metabolic activity and/or inflammation in your body. If you have absolutely no symptoms like low grade fever,sweats,joint pains,cough, urinary burning, etc, then your sed rate is purely nonspecific. On the other hand, if you're not feeling well your physician will determine what testing is appropriate after examining you.

This is a very high level, suggesting potentially serious inflammation or infection somewhere in your body. Many possible causes, can't even guess without more info. Overweight doesn't do it. You need comprehensive medical evaluation, blood counts, CRP test (another inflammatory marker), maybe other tests. Keep working with your doc; or get a second opinion if s/he doesn't evaluate further.