Beta-blockers could be helping to fuel the obesity epidemic by dampening the body's ability to burn calories and fat over the long term, researchers say in a new report.
Weight gain is a known side effect of beta blockers, particularly older ones such as atenolol (Tenormin) and metoprolol (Lopressor, Toprol-XL). Newer versions, like carvedilol (Coreg), appear to carry less risk of added pounds.
In a new study reported online in the International Journal of Obesity, Australian researchers found that among more than 11,400 adults with high blood pressure and/or diabetes, those on beta-blockers weighed more, on average, and had larger waistlines.
In a separate look at 30 patients with high blood pressure, they found that people on beta-blockers generally burned fewer calories and fat after a meal.
Less physical activity
The patients on beta blockers also reported lower physical activity levels in their day-to-day lives.
Beta blockers are suspected of curbing people's physical activity because the drugs slow the heart rate and may cause people to tire more easily.
Together, the findings suggest that beta blockers lead to weight gain by curbing people's calorie expenditure, according to the researchers, led by Dr Paul Lee of St. Vincent's Hospital in Sydney.
"Our hypothesis is that widespread use of beta blockers may fuel the modern-day obesity epidemic," Dr Lee said.
Most of the patients in the study were participating in a clinical trial looking at the effects of blood pressure lowering among people with diabetes. The rest were patients being treated for diabetes or high blood pressure at St. Vincent's.
On average, patients on beta blockers were anywhere from 11 to 37 pounds heavier, depending on the study group.
In the smaller study of patients with high blood pressure, the researchers compared calorie- and fat-burning in 11 people on beta blockers and 19 adults the same age and weight receiving different anti-hypertensives.
They found that after a meal, the beta blockers users burned roughly 30% to 50% fewer calories and fat.
"We hypothesize that chronic beta-blockade causes obesity by blunting energy expenditure," the research team concludes.
(Reuters Health, Amy Norton, March 2011)