Hello dear, Beta blocker propranolol has a known side effect to cause alteration in lipid metabolism. This can be considered as a reason for your inability to lose weight. So, as long as you are on this medication, you need to take low fat diet along with regular aerobic exercise. This will be beneficial in not only reduction of weight but also improve the functioning of your Cardiovascular system. And as the Cardiovascular functioning improves, you may not have to take the medicine at all. Kindly discuss with your treating Doctor regarding this. One more thing...please do not make hurry in losing weight. The human body functions according to its metabolic rate & any measure taken to hasten it may be harmful. Wishing you a good health. Take care.