BACKGROUND:

The elevated high-density lipoprotein (HDL) cholesterol concentrations of long distance runners has been ascribed almost exclusively to increased muscle lipoprotein lipase. Based on data collected in cross-sectional and longitudinal studies, the investigators proposed an alternative theory: long-distance runners had the HDL-cholesterol metabolism of men who were below their sedentary weight rather than the HDL-cholesterol metabolism of lean sedentary men who were at their usual sedentary weight. In other analyses, they found that the most significant determinant of male runners' plasma HDL-cholesterol concentrations was the difference between the runners' greatest weight and their current weight. HDL- cholesterol levels were highest in runners who had lost the most weight, i.e., highest in those who were presumed to be the furthest below their weight set-point

The study was a result of a Program Announcement (PA) released in October, 1994 on Physical Activity and Cardiopulmonary Health. The PA was jointly sponsored by the NHLBI, the National Institute of Diabetes and Digestive and Kidney Diseases, and the National Institute of Nursing Research.

DESIGN NARRATIVE:

In this cross-sectional study, runners and sedentary men and women were measured for lipoprotein cholesterol, triglycerides, polyacrylamide gel electrophoresis of HDL and low-density lipoprotein subclasses, apolipoproteins A-I and B, intravenous fat clearance rate, post-heparin lipoprotein lipase and hepatic lipase, adipose tissue lipoprotein lipase, cholesteryl ester transfer activity, diet, percent body fat, and regional adiposity. It was hoped that the survey would confirm or reject the weight set-point hypothesis, provide a possible explanation of the lipoprotein differences between male and female runners, and elucidate the mechanism for the lipoprotein changes that occur during exercise-induced weight loss.