This meta-study shows that forty minutes of exercise four times per week is very effective
Investigators from Tokyo published results in the May 28 issue of the Archives of Internal Medicine from a meta-analysis they performed to evaluate the effect of exercise on HDL levels. Their meta-analysis included data from 35 randomized trials assessing the effect of exercise on HDL levels in adults. While exercise regimens varied among these studies, on average patients in these studies exercised for 40 minutes, three to four times per week, and the effect on HDL was measured after eight to 27 weeks.
Across the studies, participants had increases in HDL cholesterol averaging about 2.5 mg/dL. This increase in HDL cholesterol was only modest, but was statistically significant. Furthermore, since cardiac risk is thought to drop by two to three percent for each 1 mg/dL increase in HDL, a 2.5 mg/dL rise in HDL amounts to a substantial reduction in risk.
Perhaps the most interesting finding from this study is the observation that the duration of exercise sessions - and not the frequency or intensity of exercise - correlated the best with rises in HDL levels. The investigators report that in research subjects exercising for at least 20 minutes, each additional 10-minute increase in exercise duration increased HDL levels by an additional 1.4 mg/dL.
Exercise and HDL Cholesterol - How Exercise Affects HDL Cholesterol