For some patients, there is a connection between taking beta blockers and weight gain. Though this side effect is rare and only occurs with some beta blockers, patients do occasionally report a slight increase in weight when beginning treatment with these medicines. In general, newer varieties of beta blockers do not cause weight gain, while older varieties may cause a gain of a few pounds. Changes in metabolism or a switch from a different type of medication are the most likely causes for the increase in weight after taking beta blockers.
Some of the older varieties of beta blockers can cause a slight increase in a patient's weight when the patient first begins taking this medication. Metoprolol and atenolol have been known to cause an increase of about 4 pounds (1.8kg). The connection between taking these beta blockers and weight gain is not present for all patients who are prescribed these specific beta blockers. Putting on more than a few pounds after starting beta blockers is not likely related to taking this type of drug.
Doctors aren't sure why there is a connection between these older beta blockers and weight gain. It has been speculated that this class of drugs can lower a patient's metabolism, which can decrease the rate at which the person burns off calories. The metabolic change that can occur as a result of taking beta blockers is not extreme and is generally only responsible for a patient putting on a few extra pounds.
It is also possible for a patient to experience a slight increase in weight when switching from a diuretic medication, which may be prescribed for the same health conditions as a beta blocker. Weight gain may occur when the patient switches medications because one of the side effects of many diuretic pills is that they can keep a few pounds off a patient. Though this is not a direct connection between beta blockers and weight gain, many patients are switched to these drugs after taking diuretics for a time, so a slight increase in weight is common among this group of patients.
There is no connection between most beta blockers and weight gain. Newer forms of the drugs do not include weight gain as a side effect. Most patients who are prescribed beta blockers are given these newer varieties and shouldn't expect to see any weight gain as a result of taking these medications.