Exercise, even without weight loss, improves lipid profiles

Shelley Wood

November 06, 2002

Durham, NC - Higher amounts of exercise appear to produce beneficial changes in lipoprotein profiles, even when body weight remains constant, a new study suggests. The research, which helps explain in part the reductions in cardiovascular risk with regular exercise, also implies that amount of exercise is more important than intensity of exercise, at least in terms of lipoprotein responses, the authors say.

Dr William E Kraus (Duke University Medical Center, Durham, NC) and colleagues report the results of their randomized, controlled Studies of Targeted Risk Reduction Interventions through Defined Exercise (STRRIDE) in the November 5, 2002 issue of the New England Journal of Medicine[1].

Impetus for the study comes from the fact that there are no prospective, randomized studies of exercise comparing the effects of at least 2 exercise amounts on lipid profiles, the authors observe. Moreover, emerging data indicating that size and concentration of LDL and HDL particles are important determiners of cardiovascular risk raise questions about whether exercise has any effect on lipoprotein size or on concentrations of different sizes of particles.

Lipid changes in response to exercise

Kraus et al randomized 111 overweight, sedentary men and women to either 6 months of no exercise (control group) or to 1 of 3 forms of regular exercise over 8 months. All participants had mild to moderate dyslipidemia at the study outset. Exercise groups were high amount, high intensity (equivalent to jogging 20 miles per week); high amount, moderate intensity (equivalent to jogging 12 miles per week); and low amount, moderate intensity (equivalent to walking 12 miles per week). Peak oxygen consumption in the 2 high-amount exercise groups was 65% to 80%, compared with 40% to 55% in the low-amount group.

The researchers report that all 3 exercise groups had improvements in plasma lipoprotein profiles compared with controls, including decreases in total and very low density lipoprotein (VLDL) and triglycerides, increases in size of LDL particles, and a trend toward decreased numbers of LDL particles. The high-intensity, high-amount exercise patients were the only group to show an increase in HDL cholesterol levels and an increase in HDL particle size as well as a significant decrease in the number of LDL particles.

Mean changes from baseline in plasma lipoproteins according to exercise type

Lipoprotein measurement

Low amount, moderate intensity

Low amount, high intensity

High amount, high intensity

p*

LDL cholesterol (mg/dL) +5.1 +2.1 -3.6 0.01
HDL cholesterol (mg/dL) +1.1 +.8 +3.8 0.005
Triglycerides (mg/dL) -50.4 -13.3 -20 0.002
LDL particles (nmol/L) -59 -6 -96 0.002
Small LDL particles (mg/dL of cholesterol) +4.7 +1.3 -9.8 <0.001
Size of LDL particles (nm) +0.1 +0.1 +0.3 0.05
Large VLDL particles (mg/dL of triglycerides) -42 -13.5 -14.5 0.03
Size of VLDL particles (nm) -6.5 -4.1 -1.1 0.04
Large HDL particles (mg/dL of cholesterol) +0.9 +0.9 +4.9 0.02
Size of HDL particles (nm) 0 0 +0.2 0.02
*p for intention-to-treat analysis, comparing changes in high-amount, high-intensity group with changes in control patients

The study findings suggest that the standard lipid profile used for risk assessment today (measuring total cholesterol, HDL, LDL, and triglycerides) is not comprehensive or sensitive enough in predicting cardiovascular risk.

"What we measure in the traditional lipid profile is how much cholesterol is carried in LDL particles, and how much cholesterol is carried in HDL particles, and not how each is distributed," Kraus explained to heartwire . "Other research has shown that the smaller dense LDL particles are a lot worse than the large fluffy ones. And it turns out that exercise does have significant effects on the number and the size and density of LDL particles and may explain why exercise may have a benefit on cholesterol, even though it doesn't look like it has an effect on LDL cholesterol."

Kraus believes evolving tools for measuring lipid risk will ultimately incorporate the types of factors he and his colleagues measured. "In the future, I think the standard lipid panel will employ size and number determinations, in addition to total cholesterol."

The authors also note that effects on lipids were similar in both the moderate- and low-intensity groups doing the same amount of exercise, implying that the intensity of the exercise was secondary to the volume of exercise performed, at least in terms of lipid profile.

"There are other parameters of CV risk that are affected by exercise, such as insulin resistance and fat mass," Kraus commented. He pointed out that the study reported only weight, not fat and muscle mass. "Although the people in this study had no difference in their weight change, people exercising at higher intensity gained more muscle and lost more fat. So we can tell you that exercise intensity didn't seem to matter for lipids, but it may matter for something else."

Ray of hope for overweight people

In an editorial accompanying the study, Dr Alan R Tall (Columbia University, New York) describes some of ways in which changes in lipoprotein particles resulting from exercise might potentially be beneficial but cautions that evidence in humans is lacking[2].

"It is possible but unproved that there is a benefit of changes in the size of LDL particles, and such changes are likely to be less important than changes in VLDL and LDL cholesterol and apolipoprotein B levels," he concludes. "The ensemble of changes is likely to be beneficial, even though the role of each individual component is debatable."

One thing the study does offer, he says, is "a ray of hope for those who find it easier to exercise than to lose weight."

Kraus echoed this point to heartwire . "The message from this paper for people who are really interested in risk is that they should think about measuring particle size and number if they're really interested in separating, with greater accuracy, the risk profile. However, the message for the common practicing physicians, who have people come into their offices and want to know what they can do as far as exercise is concerned for their cholesterol, is to tell them to do anything. Inactivity is really hazardous to your health, and the more you can do the better. And don't look at the scale! You're still going to get benefit from exercise, even if you don't lose weight."

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