Overweight people might be pleased with a new U.S. study that shows they do not need to lose weight to improve the cholesterol levels in their blood. However, they must exercise.
But, low intensity exercise seems to be just as good as high intensity as long as there is enough of it.
For the first time, researchers at Duke University in North Carolina have shown that exercise without weight loss has a positive impact on cholesterol.
Cholesterol is an energy-rich fat that nourishes body tissues as it is carried through the blood attached to protein particles. High levels have been linked to heart disease. It can collect on the inner walls of blood vessels, reducing or blocking the flow of blood.
In The New England Journal of Medicine, the Duke University team shows that overweight, sedentary men and women with high cholesterol levels improved their cholesterol profile when they exercised on stationary bicycles or treadmills for eight months, doing the equivalent of jogging 32 kilometers a week. This was true, despite maintaining their original weight as instructed.
"Although we do not advocate not losing weight, one should not focus on weight loss as a major benefit of an exercise program," the research leader, physician William Kraus said. "Be assured individuals who don't lose weight with exercise are still obtaining benefit,"
Dr. Kraus also says those in the group that performed the equivalent of running 32 kilometers a week improved their cholesterol profile more than another group that exercised 60 percent as much, but at the same intensity. A third group that exercised even less had the least improvement. But a fourth that did not exercise at all had worse cholesterol than at the start of the study.
"Any exercise is better than none, but more quantity per week, not necessarily more intense exercise, is better than less exercise with respect to improving your cholesterol profile," Dr. Kraus said.
To heart doctor Alan Tall of Columbia University in New York, the study provides a ray of hope for people who find it easier to exercise than to lose weight.
"In previous studies where those beneficial changes in the blood were seen, they were correlated pretty well with loss of body fat," Dr. Tall said. "But in this study, they were able to detect pretty large effects even without body weight loss.
The improvement was not necessarily in lower levels of the bad form of cholesterol known as LDL, but changes in the number and density of the size of the LDL particles. The researchers showed that increasing amounts of exercise increased the particle sizes, making them fluffier. Dr. Kraus at Duke University says this is considered healthier, possibly because they break up more easily in the blood or do not get trapped in small crevices in blood vessels.
He says the study shows it is better to measure the bad cholesterol this way rather than measure its total amount.
"Many clinicians are confused because they will see two patients come in with the same LDL cholesterol with very different cardiovascular outcomes. One has heart disease and one does not," Dr. Kraus explained. "If one is able to look at the particle size and number, often those differences become clear that the individual with heart disease is carrying his cholesterol in smaller, dense particles.
To keep it all very simple, Dr. Kraus recommends overweight people cover 32 kilometers a week either by jogging or walking or doing three and a half to four hours of some other exercise.