Interaction of physical activity and diet: implications for lipoprotein metabolism.

OBJECTIVE: To consider how physical activity interacts with diet to modify lipoprotein metabolism and comment on implications for human health.
DESIGN: An overview of lipoprotein metabolism is followed by a summary of the main effects of physical activity on lipoprotein metabolism. Interactions with dietary practice and the disposition of dietary lipid are reviewed, with comment on links with body fatness.
SETTING: Literature is reviewed in relation to the risk of atherosclerotic disease.
SUBJECTS: Although some data are presented on athletic groups, evidence relating to individuals with normal physical activity habits is mainly discussed.
RESULTS: Physical inactivity is a risk factor for cardiovascular disease and one mechanism may involve changes to lipoprotein metabolism. The consensus is that aerobic activity involving an expenditure of > or = 8 MJ week(-1) results in an increase in HDL cholesterol and probably decreases in fasting triacylglycerol. These changes Occur despite the spontaneous increase in the proportion of dietary energy from carbohydrate which accompanies increased exercise. For this reason, exercise may be a means of reducing the hypertriglyceridaemic and HDL-lowering effects of low fat (high carbohydrate) diets. Decreases in total and low density lipoprotein cholesterol are sometimes, but not always, reported in sedentary individuals beginning exercise. One mechanism linking all these changes may be alterations to the dynamics of triacylglycerol-rich particles, particularly in the fed state.
CONCLUSION: The expenditure of considerable amounts of energy through regular, frequent physical activity increases the turnover of lipid substrates, with effects on their transport and disposition which may reduce the progression of atherosclerosis.