We studied ten male distance runners before and after a marathon to determine the effects of prolonged exercise on serum lipoprotein values and the capacity to clear plasma triglycerides. Serum lipid and lipoprotein concentrations, intravenous fat clearance, and postheparin plasma lipolytic activities were measured 24 hours before and 18 hours after the race. The clearance rate of exogenous fat increased 76% ± 64%, postheparin lipoprotein lipase activity increased 46% ± 35%, and fasting triglyceride levels decreased 26% ± 13% after the race. High-density lipoprotein (HDL) cholesterol level increased 10% ± 8%, primarily due to a 19% ± 17% increase in the HDL2 subfraction. Changes in the clearance rate of exogenous fat were directly related to changes in HDL cholesterol level and the HDL2 subfraction. Thus the rise in HDL cholesterol concentrations after prolonged exercise may be a consequence of enhanced fat clearance.
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