Effects of Amount and Intensity of Excercise on Plasma Lipoproteins
Summary written by Kevin Fontaine, Ph.D.
It is well known that physical activity is associated with reduced risk of cardiovascular disease (CVD), possibly because physical activity may improve lipid profile. However, even if this were the case, it is unknown how much and how intense the physical activity has to be to produce optimal benefit. To address this, Kraus and colleagues conducted a prospective, randomized study to investigate the effects of the amount and intensity of exercise on lipoproteins (NEJM 2002; 347:1483-1492).
Methods: One hundred and eleven sedentary, overweight adults with mild-to-moderate dyslipidemia were randomized either to a 6-month control group or to 8 months of one of three exercise conditions (high amount-high intensity: [equivalent of jogging 20 miles per week at 65-80% of peak oxygen consumption], low amount-high intensity: [equivalent of jogging 12 miles per week at 65-80% of peak oxygen consumption], or low amount-moderate intensity: [equivalent of jogging 12 miles per week at 40-55% of peak oxygen consumption]). To control for the confounding effects of weight loss, participants were counseled to maintain their weight. Detailed lipoprotein profiles were obtained by nuclear magnetic resonance spectroscopy and were verified by measuring cholesterol in lipoprotein subfractions.
Results: Eighty-four participants complied with the respective protocols. Although the exercise training had no effect on either total cholesterol or low-density lipoprotein (LDL) concentrations, the beneficial effects of exercise on lipoprotein subfractions were seen in all exercise conditions, but the effect was most pronounced in the high amount-high intensity condition. Specifically, high amount-high intensity exercise significantly reduced LDL concentrations and small LDL particles and increased the average size of LDL particles. Similar effects were seen on the other lipoprotein subfractions (high-density lipoprotein [HDL], very-low-density lipoproteins [VLDL]) studied. Similar, though smaller effects on lipoproteins were seen in both the lower amount of exercise conditions. The intensity of exercise was less important, at least in the lower amount of exercise conditions. Finally, changes in lipoprotein profiles were largely independent of improvements in fitness.
Conclusion: The highest amount of weekly exercise had beneficial effects of a variety of lipoprotein profiles, independent of weight change, intensity of exercise, or improvements in fitness.
Editorial Comment: This study provides additional support for the health benefits of staying physically active. In this case, significant improvements in lipoprotein profiles and subfractions were seen in all three exercise conditions compared to controls. The benefits were independent in changes in weight or improvements in fitness. More importantly, although the high amount-high intensity exercise group produced the greatest benefits, both high and lesser amounts of lower intensity exercise were also shown to be beneficial. This suggests that the intensity of exercise may be less important than is the amount of exercise. Thus, being physically active, whether through exercise training or by staying as active as possible throughout the day may significantly improve lipoprotein profiles and reduce CVD risk.