Lipid outcomes from supervised exercise interventions in healthy adults.

Cardiovascular disease remains the leading cause of death in the United States today.1 Hyperlipidemia is a well-established risk factor for cardiovascular disease.1-3 Control of lipid levels is one of the key strategies for primary and secondary prevention of cardiovascular disease.2 While pharmacologic approaches to lipid management are available, non-pharmacological treatments are the preferred and first-line approach to managing hyperlipidemia, particularly for primary prevention.4 Exercise is any structured, planned, bodily movement to increase or maintain physical fitness.5 Exercise is a key health behavior intervention to improve lipid levels and lower cardiovascular disease risk. Many trials have examined exercise interventions to improve lipid outcomes, with varying results.6,7 While a link has been established between weight loss and improved lipid levels,8 more recent work indicates that exercise may improve lipid levels independent of weight loss.9,10 Even among healthy adults, too few individuals engage in regular physical exercise. Only 48.4% of persons age 18 years and older obtain the recommended amount of aerobic exercise.11 Even individuals considered as healthy are frequently not active enough to meet the recommended levels of exercise to reduce the risk of developing chronic disease. Health care providers should play a key role in assisting individuals, particularly those at greater risk for cardiovascular disease, to increase the quantity and quality of their exercise behavior. Supervised exercise interventions, where participants exercise at a specified location under the supervision of an interventionist (eg, exercise researcher, trainer), have been effective at improving exercise behavior among healthy adults.12 The lipid-lowering effect of supervised exercise programs for healthy adults, however, has not been conclusively established. Several recent literature syntheses have focused on the impact of exercise interventions on lipid outcomes.9,10,13-21 These studies have established the benefit of exercise overall as a component of lipid control for participants with cardiovascular and metabolic risk factors10,18,19,22 but the strength of the evidence for the effects of exercise on lipid outcomes for healthy adults is less clear. Published meta-analyses reporting lipid outcomes of exercise for healthy adults have mostly focused on specific sub-populations or limited intervention types. These meta-analyses have each synthesized small numbers of studies (ranging from 6 to 35 trials), and have had conflicting findings regarding the exercise characteristics associated with significant improvement in lipid levels. Finally, none of the meta-analyses identified in the past ten years examined the effect of supervised exercise on lipid outcomes of healthy adults. This systematic review and meta-analysis aims to synthesize the results of supervised exercise interventions in populations of healthy adults, and to conduct moderator analyses to determine whether particular sample, study, or intervention characteristics are associated with greater improvement in lipid outcomes.