A 90-minute walk lowered triglycerides and improved blood vessel function in a small group of lean and obese men, and the benefits persisted into the following day, even after participants ate a fatty meal, according to a new study in the Dec. 21, 2004 issue of the Journal of the American College of Cardiology.
“Just one brisk walk substantially improved blood vessel function both before and during the hours after eating a fatty meal, and the exercise improved the body’s handling of dietary fat to the same extent irrespective of whether someone was lean or obese,” said Jason M. R. Gill, Ph.D., at the University of Glasgow, Scotland.
“The differences observed in blood fat levels and in blood vessel function following just one workout are remarkable, particularly as these were evident for at least 24 hours after completion of exercise,” he said. “Recent research has shown that blood vessel function is impaired for a few hours after eating fatty food, and this may be one reason why the rise in blood fats seen after eating seems to contribute to the development of heart disease. As we have known for some time that exercising before eating fatty food reduces this rise in blood fat levels, we thought that a workout before eating a fatty meal could help to prevent the post-meal decline in blood vessel function.”
The researchers studied 10 lean and 10 obese middle-aged men. Each man was tested twice for his response to a fatty meal, with the tests performed a week or two apart. On the afternoon before one of the tests, each man walked on a treadmill for 90 minutes. No exercise was done the day before the other test.
Exercise reduced triglyceride concentrations by 25 percent both before and after the fatty meal. Similar responses were seen in both the lean and the obese men.
Particularly striking, according to Dr. Gill, was the effect of the long walk on the functioning of tiny blood vessels in the forearms of subjects as measured by laser Doppler imaging. Overall, the responsiveness of the endothelium, measured before the fatty meal, was 25 percent better following the treadmill walk. The endothelium is a single layer of cells that lines the inner wall of blood vessel. It provides an important defense against the build-up of fatty deposits inside blood vessels.
Although the fatty meal reduced blood vessel function whether or not the men had exercised the previous afternoon, the decline was not as great after exercise. Endothelium-dependent function was 15 percent higher and endothelium-independent function was 20 percent higher in the exercise trial than in the control trial, and again the benefits were seen in both the lean and obese men.
While the benefits of regular physical activity are well-established, the researchers say this study suggests some possible explanations for the protective effects: that exercise can both improve the way the body metabolizes food and help blood vessels resist the harmful effects of fatty foods. This trial also demonstrated that a single exercise session can provide immediate benefits that last at least a day.