Statins, the most widely prescribed drugs worldwide, are often suggested to lower cholesterol and prevent heart disease in individuals with obesity, diabetes and metabolic syndrome, which is a combination of medical disorders including excess body fat and/or high levels of blood pressure, blood sugar and/or cholesterol.
"Daily physical activity is needed to maintain or improve fitness, and thus improve health outcomes. However, if patients start exercising and taking statins at the same time, it seems that statins block the ability of exercise to improve their fitness levels," said John Thyfault, an associate professor of nutrition and exercise physiology at MU.
Thyfault said that many cardiologists want to prescribe statins to all patients over a certain age regardless of whether they have metabolic syndrome; the drugs also are recommended for people with Type 2 diabetes. He recommends that cardiologists more closely weigh the benefits and risks of statins given this new data about their effect on exercise training.
Thyfault and his colleagues measured cardiorespiratory fitness in 37 previously sedentary, obese individuals ages 25-59 with low fitness levels. The participants followed the same exercise regimen on the MU campus for 12 weeks; 18 of the 37 people also took 40 mg of simvastatin daily.
Statins significantly affected participants' exercise outcomes. Participants in the exercise-only group increased their cardiorespiratory fitness by an average of 10 percent compared to a 1.5 percent increase among participants also prescribed statins.
Additionally, skeletal muscle mitochondrial content, the site where muscle cells turn oxygen into energy, decreased by 4.5 percent in the group taking statins while the exercise-only group had a 13 percent increase, a normal response following exercise training.
Thyfault suggests that future research determine whether lower doses of simvastatin or other types of statins similarly affect people's exercise outcomes and thus their risk for diseases such as Type 2 diabetes.
Starting a statin regimen after exercising and obtaining a higher fitness level may reduce the drugs' effects on fitness, he said.
The study was published in the Journal of the American College of Cardiology.