Aerobic Exercise, Diet and Cholesterol: A Meta-Analysis

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Less than optimal lipid and lipoprotein levels are a major risk factor for cardiovascular disease morbidity and mortality. Aerobic exercise and a prudent diet, defined as a diet that is low in saturated/trans fat and cholesterol and/or high in fiber have been recommended for improving lipid and lipoprotein levels in adults. Unfortunately, randomized controlled trials that have examined the combined effects of these low-cost lifestyle changes have led to less than overwhelming results while narrative reviews on this topic have led to conflicting conclusions. Consequently, the overall magnitude and direction of effect, as well as the relationships among such variables as subject, diet, and training program characteristics and how they contribute to changes in lipids and lipoproteins, are not clear. Meta-analysis, one of the highest forms of evidence for decision-making, is a method of pooling the results of separate studies. It is a quantitative approach for increasing statistical power of primary end points, resolving uncertainty when studies disagree, improving estimates of treatment effect, and answering questions not posed at the start of individual trials. To date, no study has quantitatively synthesized (meta-analyzed) the existing literature in relation to the combined effects of aerobic exercise and a prudent diet on lipid and lipoprotein levels in adults. Therefore, the specific aims of this proposed two-year project are to use the meta-analytic approach to (1) determine the overall effects of aerobic exercise and a diet that is low in saturated/trans fat and cholesterol and/or high in fiber on lipid and lipoprotein outcomes in adults, and (2) identify the relationship between selected characteristics and changes in lipids and lipoproteins as a result of aerobic exercise and a diet that is low in saturated/trans fat and cholesterol and/or high in fiber in adults. The results of this project will provide a solid scientific foundation from which first-time quantitative recommendations, based on the meta-analytic approach, will be made regarding the combined effects of aerobic exercise and a prudent diet on lipids and lipoproteins in adults. This is important since one of the major goals of the Department of Health and Human Services is to increase the quality and years of healthy life.