Chronic, dynamic exercise is associated with increased circulating levels of high-density lipoproteins (HDLs) and reduced low-density lipoproteins (LDLs), such that the ratio of HDL to total cholesterol is increased. These changes in cholesterol fractions occur at any age if exercise is regular. Weight loss and increased insulin sensitivity, which typically accompany increased chronic physical activity in sedentary individuals, undoubtedly contribute to these changes in plasma lipoproteins. Nonetheless, in people with lipoprotein levels that place them at high risk for coronary heart disease, exercise appears to be an essential adjunct to dietary restriction and weight loss for lowering
LDL cholesterol levels. Because exercise acutely and chronically enhances fat metabolism and cellular metabolic capacities for (3-oxidation of free fatty acids, it is not surprising that regular activity increases both muscle and adipose tissue lipoprotein lipase activity. Changes in lipoprotein li-pase activity, in concert with increased lecithin-cholesterol acyltransferase activity and apo A-I synthesis, enhance the levels of circulating HDLs.
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