We propose to further our studies on the effects of exercise an weight loss on lipoprotein through the analysis of high-density (HDL) and low- density lipoprotein (LDL) subclasses from nondenaturing polyacrylamide gradient gel electrophoresis. Our experience suggests that exercise and weight loss affect specific lipoprotein subclasses, and that identifying the affected subclasses is fundamental to understanding the metabolic and health benefits exercise and weight loss. HDL may be divided into two HDL2 and three HDL3 subclasses that are approximated by their estimated particle diameters: HDL3c (7.2-7.8 nm), HDL3b (7.8-8.2 nm), HDL3a (8.2- 8.8 nm), HDLa (8.8.-9.7 nm) and HDL2b (9.7-12.9 nm). Seven LDL subclasses have also been identified: LDL-IVB (22.0-23.3 nm), LDL-IVA (23.3-24.1 nm), LDL-IIIB (24.2-24.6 nm), LDL-IIIA (24.7-25.5 nm), LDL-II (25.5-26.4 nm), LDL-I (26.0-28.5 nm) and intermediate density lipoprotein (IDL 28.0-30.0 nm). In addition, an LDL profile with a major peak less than or equal to 25.5 nm characterize a type-B LDL phenotype, which appears to be inherited by a dominant allele with a gene frequency of about 0.25 that is located near the LDL-receptor locus on chromosome 19. The plasma samples were collected during three randomized controlled clinical trial. The following hypotheses will be examined: 1. Do exercise or dieting affect specific HDL and LDL subclasses and promote greater conversion of LDL phenotype B to phenotype A as compared to control? 2. Does weight loss by exercise have the same effect on HDL and LDL subclasses and LDL phenotype as weight loss by dieting? 3. Do changes in weight, regional adiposity or body fat account for the changes in HDL and LDL subclasses and LDL phenotype in exercisers and dieters vis-a-vis controls? 4. Are changes in HDL and LDL subclasses during dieting the same in men and women? 5. Do baseline HDL and LDL-subclasses and LDL-phenotype identify persons most likely to increase HDL or decrease LDL during exercise or dieting?