For blood pressure, can you be fit but fat?

As expected, the study found that overweight or obese people were more likely to have a high systolic blood pressure - the top number in a blood pressure reading. But for those with a high body mass index (BMI) - a measure of weight versus height -- how in shape they were only had a small impact on their blood pressure.

The results suggest that people who are trying to decrease their risk for high blood pressure should focus on losing weight however they can most effectively do that, the authors say, and that increasing physical fitness should be a secondary goal.

"Obesity is such a strong predictor of blood pressure or hypertension risk that having a normal body weight is really what's going to drive your blood pressure" rather than your fitness level, Dr. Susan Lakoski, a cardiologist at the University of Texas Southwestern Medical Center and one of the study's authors, told Reuters Health.

At least in terms of lowering your risk for high blood pressure, she said, "it's not realistic to be fit and fat."

One in three American adults has high blood pressure - above 140/90 - including more than half of those over 55. Having high blood pressure puts a person at greater risk for stroke, heart attack, and kidney disease.

The Centers for Disease Control and Prevention reports that high blood pressure will cost the U.S. more than $75 billion in 2010 - from hospital stays and doctors' appointments, drugs, and lost time at work. Doctors often recommend medication and lifestyle changes, including exercise, for patients with high blood pressure.

In the study, published in the American Heart Journal, Lakoski and her colleagues analyzed data from approximately 35,000 patients, mostly white men, collected over the last 20 years at the Cooper Clinic in Dallas, Texas. When patients came into the clinic, doctors measured their body composition, blood pressure, and fitness levels.

To determine how fit patients were, the doctors timed how long they could keep up a comfortable walking pace on a treadmill at varying inclines and speeds.

Using this data, the authors compared BMI, fitness levels, and systolic blood pressure of all patients to see if the three measurements were linked. Among all participants, having a higher BMI was associated with having a higher systolic blood pressure, a correlation that has been found many times in the past.

But being fit had less of an effect on systolic blood pressure readings than BMI, and when the authors looked at people of the same age and gender, fitness didn't seem to have any effect on blood pressure.

Only people of normal weight seemed to get much of a blood pressure benefit from having better fitness levels - possibly because fitness alone couldn't overcome the negative effects of being obese, Lakoski said.

That doesn't mean that people who are overweight shouldn't try to improve their fitness, said Dr. Paul McAuley, who teaches health education at Winston-Salem State University in North Carolina. McAuley pointed out that the study is only a snapshot of one group of people at one time. The study doesn't show how the participants fared over the long term.

His research has shown that people who are obese but fit aren't any more likely to die from heart disease and stroke - or any cause - than people who are thinner and fit.

"We've got to back off and say, 'what is blood pressure measuring?'" McAuley told Reuters Health. "It's an indicator just like a weatherman would use. It's not the disease itself."

Whether or not being in better shape affects a person's blood pressure, McAuley said, "fitness does something to prevent disease and mortality."

Lakoski agreed that for overall health and mortality risk, fitness is an important part of the picture. "The ultimate thing we'd like to see is people obtain a lean body weight and start improving their fitness in the real world," she said.

Dr. Tim Church, the former head of medical research at The Cooper Institute who now studies exercise and disease at Louisiana State University's Pennington Biomedical Research Center, told Reuters Health that the findings don't change the current thinking on exercise and long-term health.

"Being overweight is bad for you (and) being sedentary is bad for you," he said.

SOURCE: link.reuters.com/duc89m American Heart Journal, July 2010.