Exercising may override the effect of being overweight or obese on heart attack or stroke in middle-aged and elderly people, according to research published today in the European Journal of Preventive Cardiology.

The study included more than 5,000 people aged 55 years and older who were followed for 15 years.

"Overweight and obesity is associated with a higher risk of cardiovascular disease and it is recommended to lose weight," said study author Dr. Klodian Dhana of Rotterdam's Erasmus University Medical Center. "But in the elderly this is slightly different because weight loss, especially unintentional, is associated with muscle loss and death."

"Physical activity is associated with a lower risk of cardiovascular disease regardless of age," he continued. "We investigated the combined impact of body mass index (BMI) and physical activity on cardiovascular disease in the middle age to elderly population."

Participants were categorized by BMI: normal weight (18.5-24.9), overweight (25-29.9) and obese (>30). They were also divided into two groups by physical activity — low or high.

During the 15-year follow-up, 16 percent had a heart attack or stroke. Physical activity was associated with a decreased risk of cardiovascular disease regardless of BMI category. There was no association between BMI alone and cardiovascular disease.

"In the overall population we found that physical activity was protective for cardiovascular risk," said Dhana. "Overweight and obese participants were not at increased cardiovascular risk compared to those of normal weight."

The researchers analyzed the joint effect of physical activity and BMI. Compared to normal weight people with high physical activity levels (the ideal), overweight or obese individuals with high levels of physical activity were not at increased risk of cardiovascular disease. However, overweight or obese people with low levels of physical activity had 1.33 and 1.35 times higher risk for developing cardiovascular disease, respectively.

"Our results show that physical activity plays a crucial role in the health of middle age to elderly people," said Dhana. "Those who are overweight and obese without adequate physical activity are at higher risk of developing cardiovascular disease."

"People who engage in high levels of physical activity are protected from the harmful effects of adipose tissue on cardiovascular disease," he said. "This may be why we found that the beneficial impact of physical activity on cardiovascular disease outweighs the negative impact of BMI."

Being overweight can have cardiovascular advantages. Another study released in January found that people who were overweight or obese were more likely to survive heart surgery than those of normal weight. Patients who were underweight had the highest risk of dying.

The study, which was conducted by the University of Leicester and published in the journal Circulation, found that patients of normal weight were almost twice as likely to die in the hospital following heart surgery as those who were overweight or obese— 4.4 percent compared to 2.8 percent who were overweight and 2.7 percent who were obese. However, 8.5 percent of those who were underweight died.

According to the American Heart Association, cardiovascular diseases, including heart attack and stroke, account for one out of every three deaths in the U.S.