A meta-analysis was used to analyze 95 studies conducted between September 1955 and October 1983 that measured changes in human serum lipid and lipoprotein levels in response to exercise training. Changes in body weight during exercise training may confound observed changes in lipid and lipoprotein levels; Therefore, data from these studies were classified as subjects gaining weight, maintaining weight, or losing weight. The results showed different changes in cholesterol, triglycerides, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol, and cholesterol/high-density lipoprotein cholesterol levels among the three weight categories. In the absence of changes in body weight, cholesterol and LDL-C levels decreased significantly (7.3 mg per deciliter and 3.3 mg per deciliter, respectively). Cholesterol and LDL-C levels also decreased significantly when weight was lost (13.2 mg per deciliter and 11.1 mg per deciliter, respectively). However, cholesterol and LDL-C levels increased 2.9 mg per deciliter and 3.0 mg per deciliter, respectively, with weight gain. These results indicate that the greatest reduction in cholesterol and LDL-C levels occurred when exercise training was combined with weight loss.