Eeyore,
Beta blockers in general, because they slow down heart rate, make it more difficult to lose weight. Studies show that COREG, in clinical trials, causes a relatively high percentage of people to actually gain weight on it.
Are you taking it for hypertension? Congestive heart failure?
Talk to your doctor about this. If you are taking it for the former, there are many other alternatives out there for you. I don't know enough about CHF to recommend anything except, as I said, speak to your doc.
zuzu xx