The purpose of this study was to determine the threshold of exercise energy expenditure necessary to change blood lipid and lipoprotein concentrations and lipoprotein lipase activity (LPLA) in healthy, trained men. On different days, 11 men (age, 26.7 +/- 6.1 yr; body fat, 11.0 +/- 1.5%) completed four separate, randomly assigned, submaximal treadmill sessions at 70% maximal O2 consumption. During each session 800, 1,100, 1,300, or 1,500 kcal were expended. Compared with immediately before exercise, high-density lipoprotein cholesterol (HDL-C) concentration was significantly elevated 24 h after exercise (P < 0.05) in the 1,100-, 1,300-, and 1,500-kcal sessions. HDL-C concentration was also elevated (P < 0.05) immediately after and 48 h after exercise in the 1,500-kcal session. Compared with values 24 h before exercise, LPLA was significantly greater (P < 0.05) 24 h after exercise in the 1,100-, 1,300-, and 1,500-kcal sessions and remained elevated 48 h after exercise in the 1,500-kcal session. These data indicate that, in healthy, trained men, 1,100 kcal of energy expenditure are necessary to elicit increased HDL-C concentrations. These HDL-C changes coincided with increased LPLA.