Weight gain when taking Bisoprolol (10 - 12.5 mg daily)

I was first prescribed Bisoprolol in November 2005, starting with a daily dose of 2.5 mg. Since then the dose has progressively been increased to the present level of 10 to 12.5 mg in December 2006.

I have put on 35 lbs since I started taking this drug, and my weight continues to rise. Throughout this time I have kept to a very rigid diet.

What can I do to control my weight ? My cardiologist says that bisoprolol is the only suitable drug with which to treat me.